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Digitized by tine Internet Arciiive 
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Tine Library of Congress 



http://www.arcliive.org/details/oceanatmospherelOOrecl 



/ 



THE OCEAN, 

ATMOSPHERE, AND UfE. 

BEING THE SECOND SERIES OF A 

descriptive history of the life of the globe. 
By ELISEE RECLUS, 

AUTHOR OF "THE EARTH," ETC. • 



ILLUSTRATED WITH TW(3 HUNDRED AND FIFTY MAPS OR FIGURES, 
AND TWENTY- SEVEN MAPS PRINTED IN COLORS. 








NEW YORK: A. 
HARPER & BROTHERS, PUBLISHERS, 

FRANKLIN SQUARE. 
1873. 



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CONTENTS. • 

PAET I. — THE OCEAN. 
BOOK I.— THE SEAS. 

Page 

Chapter I. — General Considerations 17 

Chapter II. — Oceanic Basins. — Depth of the Seas. — Lev%l of the Surface of the Ocean 20 

Chapter III. — Composition of Sea-water. — Specific Weight. — Salt Marshes, Natural 
and Artificial. — Various Substances. — Differences of Saltness. — Marine Salt 35 

Chapter IV. — Various Colors of Sea-water. — Reflections, Transparency, and Proper 
Color. — Temperature of the Depths of the Sea 41 

Chapter V. — Formation of Ice. — Ice-floes, Fields of Ice, and Icebergs. — Ice in the 
Baltic and tlie Black Sea : 46 

Chapter VI. — Waves of the Sea. — Regular and Irregular Undulations. — Height of 
the Waves. — Their Size and Speed. — Ground-swell. — Coast-waves .".... 59 

BOOK II.— CURRENTS. 

Chapter VII. — Great Movements of the Sea. — General Causes of Currents. — The Five 
Oceanic Rivers 67 

Chapter VIII. — The Gulf Stream. — Influence of this Current on Climate. — Its Im- 
portance to Commerce 70 

Chapter IX. — Currents of the South Atlantic and the Indian Ocean. — Double Eddy 
of the Pacific Ocean 82 

Chapter X. — ^Lateral Eddies. — Rennell's Current. — Counter-current in the Sea of the 
Antilles. — Equilibrium of the Waters m tlie Baltic, the Bosporus, at th^Entrances to 
the Mediterranean and the Red Sea. — Exchange of Water and Salt between the Seas 88 

» 

BOOK III.— THE TIDES. 

Chapter XL — Oscillations of the Level of the Seas. — Theory of the Tides 94 

Chapter XII. — Theory of Whewell on the Origin and Propagation of Tidal Waves. — 
Origin of the Tide in each OceBiic Basin. — " Estabhshment " of Ports. — "Co-tidal" 
Lines^ 102 

Chapter XIII. — Apparent Irregularities of the Tides. — Extraordinary size of the Tidal 
Wave in certain Bays. — Interference of Ebb and Flow. — Diurnal Tides. — Inequalities 
of successive Tides. .•. 106 

Chapter XIV.— Tidal Currents. — Races and Whirlpools. — Tidal Eddies. — Eiver Tides 116 

Chapter XV. — Ebb and Flow in Lakes and Inland Seds. — Currents of the Euripus. — 
Scylla and Charybdis 122 



CONfENTS. ' 



BOOK IV.— THE SHORES AND ISLANDS. 

• Page 

Chapter XVI. — Incessant Modifications of the Coast-line. — The Fjords of Scandinavia 
and other Countries near the Poles .' , 127 

Chapter XVII. — Filling up the Fjords by Marine and Fluvial Alluvium 133 

Chapter XVIII.— Destruction of Cliffs. — llie Coasts of the Channel. — The Straits of 
Dover. — Action of Shingle and Sand. — Giants' Caldrons. — Spouting WSlls on the 
Coasts.— Tidal Wells 139 

Chapter XIX. — Undermining of Rocks. — Varied aspect of Cliffs. — Platforms at their 
Bases. — Resistance of the Coasts. — Breakwaters formed by the Rubbish. — Heligo- 
land. — Destruction of Low Shores 147 

Chapter XX. — Normal form of Shores. — Cuitcs of " Greatest Stability." — Formation 
of New Shores. — Coast Ridges and Sand-banks. — Inland Bays 156 

Chapter XXI. — Shallows of the Coast. — Deposit from Calcareous Rocks. — Appear- 
ance of Strands and Beaches 172 

Chapter XXII. ^ — Origin of Islands. — Islands of Continental Origin. ^ — Rocks of the 
Shores. — Islands of Depression, Elevation, and Erosion. — Islands of Oceanic Origin. 
— Atolls and Volcanoes 179 

BOOK v.— THE DUNES. 

Chapter XXIII. — Dunes resulting from the Decomposition of Rocks. — Formation of 
moving Dunes on the Sea-shore. — Symmetrical Disposition of Ridges of Sand 187 

Chapter XXIV. — Height of the Hillocks. — Advance of the Dunes. — Displacement of 
' ' Etangs. " — Disappearance of Villages 195 

Chapter XXV. — Obstacles opposed by Nature to the Progress of Dunes. — Fixation of 
the Sands by Seeds 202 



PART II.— THE ATMOSPHERE AND METEOROLOGY. 
BOOK I.— THE AIR AND WINDS. 

Chapter I. — Air the Agent of the Vital Circulation of the Planet. ^ — Phenomena of Re- 
flection and Refraction. — Mirage '. 206 

Chapter II. — Weight of the Air. — Height of the Upper Strata. — Barometric Measures 213 

Chapter III. — Mean Pressure of the Atmosphere under vanous Latitudes. — Density 
of the Air in the Northern Hemisphere. — Diurnal Oscillations of the Barometrical 
Column. — Annual Oscillations. — Iri-egular Variations. — Isobarometric Lines 217 

Chapter IV. — General Law of the Circulation of Winjb. — Trade-winds from the 
North-east and South-east. — Equatorial Calms. — Oscillation of the System of Winds 223 

Chapter V. — Counter Trade-Avinds or Returning Winds 228 

Chapter VI. — The Trade-winds of the Continents. — The Monsoons. — Etesian Winds 235 

Chapter VII. — Land and Sea Breezes. — Winds from the Mountains. — Solar Breezes. 
— Local Winds. — The Simoon, Sirocco, Foehn, Tempests, and Mistral 240 

Chapter VIII. — Zone of variable Winds. — Struggle of opposing Winds. — Mean 
Direction of the Atmospheric Currents. —Law of Gyration 245 



CONTENTS. 



BOOK II.— HURRICANES AND WHIRLWINDS. 

Pap.' 

Chapter IX. — Aerial Eddies. — Cyclones of the Equatorial Regions. — The "Great 
Hurrifane " 251 

CHArxER X. — Speed of the revolving Masses of Air. — Speed of the Cyclone. — Fall of 
the Barometric Column. — Irregularities of the Wind in the Path of the Cyclone 257 

Chapter XI. — Spiral of the Hurricanes in the two Hemispheres. — Theory of Cyclones. 
— Nautical Instructions to avoid Hurricanes 263 

Chapter XII.— Eddies of Tempests.— Whirlwinds 26}» 



BOOK III.— CLOUDS AND RAINS. 

Chapter XIII. — The Vapor of Water. — The Moisture of the Air. — Absolute Moisture 
and relative Moisture 27t> 

Chapter XIV. — Formation of Mists and Clouds. — Height, Thickness, Form, and As- 
pect of Clouds 280 

Chapter XV. — Influence of the Winds on the Formation of Snow and Rain. — Distri- 
bution of Rain over Plains and Mountains 285 

Chapter XVI. — Tropical Rains. — Rainy and Dry Seasons. — Periodicity of Rains 292 

Chapter XVII. — Rains beyond the Tropics.^ — ^Winter Rains. — Rains of Spring and 
Autumn. — Summer Rains.— Rains of the Polar Regions 297 

Chapter XVIII. — Countries without Rain. — Geological action of Rains. — Contrast of 
the two Hemispheres 300 



BOOK IV.— THUNDER-STORMS, AURORAS, MAGNETIC CURRENTS. 

Chapter XIX. — Height of Thunder-clouds. — Distribution of Thunder-storms in vari- 
ous Regions of the Earth. — Cause of these Phenomena 305 

Chapter' XX. — Polar Auroras 314 

Chapter XXI. — Terrestrial Magnetism. — Declination, Inclination, and Intensity of the 
Movements of the Needle. — Magnetic Poles and Equator. — Isogonal Lines and their 
Secular, Annual, and Diurnal Variations. — Isoclinal Lines. — Isodynamic Lines 324 

BOOK v.— CLIMATES. 

Chapter XXII. — Solar Heat. — Irregularities of Local Climates. — Equalization of the 
Temperature below the Surface of the Ground 331 

Chapter XXIII. — Contrast between the Climates of the Northern and Southern Hemi- 
spheres, between those of the Eastern and Western Sides of Continents, those of the 
Coasts and the Interior of Countries, and of Mountains and Plains 335 

Chapter XXTV. — Isothermal Lines.^ — ^Thermal Equator. — Poles of Cold. — Increase of 
Temperature toward the Poles. — Open Seas 341 

Chapter XXV. — Extremes of Temperature. — Isochimenal and Isotheral Lines. — Daily 
and monthly Variations. — Decrease of Warmth in the upper Strata of the Air. — 
Variations of Climate during the Historical Period 345 



# 



10 • CONTENTS. 



PAET III. — LIFE. 
BOOK I.— THE EARTH AND ITS FLORA: 

Page 

Chapter I. — The Assemblage of living Creatures. — Number of Vegetable Species. — 
Proportion of Dicotyledons, Monocotyledons, and Cryptogams. — Forests and Savan- 
nas [ [ 356 

Chapter II. — Influence of Temperature, Moisture, and Solar Kays on Vegetation. — 
Distribution of Plants 361 

Chapter III. — Particular Habitats of Species. — Salt-water and Fresh-water Plants. — 
Littoral Species. — Parasites. — Terrestrial Species. — Influence of the Soil on Vegeta- 
tion. — Plants associated together. — Sea- weed. — Extent of Areas 368 

Chapter IV. — Contrast of the Floras in the different parts of the World. — Insular and 
continental Floras. — Increasing richness of Vegetation in the direction from the Poles 
to the Equator , 373 

Chapter V. — Distribution of Vegetation on the Slopes of Mountains. — Mingling of the 
different Floras. — Upper limits of the Plants in various parts of the World. — Irregu- 
larities in the Vertical Distribution of Plants 379 

Chapter VI. — Unconnected Species. — Displacement of Areas in consequence of Geo- 
logical Changes. — Plants of Great Britain. — Naturalization. — Incessant Modification 
of Floras 386 

BOOK II.— THE LAND AND ITS FAUNA. 

Chapter VII. — Origin of Life. — Species of Animals. — Multitude of Organisms. — Con- 
trasts of Land and Sea , 393 

Chapter VIIL— The Oceanic Fauna 396 

Chapter IX. — Influence of Climate and physical Conditions on the Species of Animals 401 

Chapter X. — Food of Animal Species. — Contrast of Faunas. — Areas of Habitation.— 
Changes in the Surface of the Areas. — Birth and Disappearance of Species 406 

Chapter XI. — Great Terrestrial Faunas. — Homoiozoic Zones 411 

Chapter XII. — Distribution of Species on the Slopes of Mountains and in the Depths 
of the Sea..... .* 416 

Chapter XIII. — Geological Labors of certain Animal Species. — Coral Reefs and Islands 421 

BOOK III.— EARTH AND MAN. 

Chapter XIV. — The Influence of Nature on the Destiny of Mankind. — Antiquity oft 
th^ Human Race on the Earth. — Monogenists and Polygenists. — Fusion of Human 
Races 434 

Chapter XV. — Influence of Climate. — Tropical Zone. — Frigid Zone. — Temperate Zone 440 

Chapter XVI. — Influence of the raised Outline of the Earth on Mankind. — Table- 
lands, Mountains, Hills, and Plains , 445 

Chapter XVII. — Influence of the Sea and running Waters. — Traveling and Commer- 
cial Nations. — Islands and Islanders...- 452 



• 



CONTENTS. 11 

PaRo 

Chapter XVIII. — Blending of different Climates. — The Influence of Civilization on 
the Featm-es of a Country 456 

Chapter XIX. — The course of History. — Harmony existing between Countries and 
the Nations inhabiting them 4G1 

BOOK IV.— THE WORK OF JIAN. 

Chapter XX. — Reaction of Man on Nature. — Exploration of the Globe. — Voyages of 
Discovery. — Ascents of Mountains 466 

Chapter XXI. — Reclamation of the Earth by Cultivation. — Ancient and modern Ir- 
rigation 470 

Chapter XXII. — The Culture of Marshes. — Drainage of the Ground in the Country 
and Towns 474 

Chapter XXIII. — The Draining of Lakes and Inlets of the Sea. — The Lake of Copais, 
the Lake of Fucino, the Sea of Haarlem, the Zuyder Zee. — Polders. — The Purifica- 
tion of Saline Marshes 478 

Chapter XXIV. — Dikes on the Sea-shore. — Points of Defense. — Point-de-Grave 487 

Chapter XXV. — Natural and artificial Ways of Communication. — Sea-shores, Des- 
erts, and Savannas. — Rivers, Canals, and Railways. — Bridges and Viaducts. — The 
cutting through Isthmuses. — The Suez Canal. — The Isthmuses of Central America... 495 

Chapter XXVI. — The industrial Power of Man. — The Electric Telegraph. — Posses- 
sion taken of the Sea. — Cultivation of Oysters 504 

Chapter XXVII. — Comparative Harmlessness of Hurricanes. — Prevision of Weather. 
— Modification of Climates effected by the Labor of Jian 510 

Chapter XXVIII. — Influence of Man on the Flora and Fauna of a Country. — En- 
croachment effected by the more common Species. — Extension given by Agriculture 
to certain cultivated Species '. 516 

Chapter XXIX. — Influence of Man on the Beauty of the Earth. — Disfigurement and 
Embellishment of the Land. — The diverse Action of different Nations. — The Appre- 
ciation of Nature. — The Progress of Mankind 522 



ILLUSTRATIONS. 

[The Colored Maps, indicated in the list by capital letters, were printed in England, and by 
mistake were in txco instances incorrectly numbered. They are located, hoicever, in their proper 
places with reference toihe text.'\ 



Number Page 

I. Straits OF Dover 21 

1. Gulf of Cape Breton 22 

2. Depths of the Adriatic 24 

;'.. Profile of Bed of Adriatic 25 

II. Submarine Platjiau 26 

4. Profile of Bed of North Sea 26 

.".. Depths of the English Channel 27 

<;. Profile of the greatest Depth 27 

III. North Atlantic Ocean 28 

7. Section of Atlantic in Tropics 28 

H. Depths at the ]\Iouth of the Ganges. . 31 

'.). Comparative Saltness of Seas 36 

10. Salt Marshes of Bessarabia 38 

1 1 . Temperature of Sea-water 44 

12. Glacier of La Madeleine 49* 

13. Course of the Icebergs 53 

IV. Antarctic Land 54 

14. Icebergs of the Antarctic Ocean 54 

15. Icebergs of tlie Antarctic Ocean 54 

16. Route of the Peacock in Ice-pack 65 

17. Course of Icebergs 56 

18. Rollings of a Ship 60 

19. Average Heights of Waves 61 

20. Average Amplitude of Waves 62 

21. Bay of St. Jean de Luz 65 

V. Current of the Gulf Stream. . 70 

22. Channel of Florida 72 

23. Route of Steam-packets 80 

VI. Oceanic Currents 84 

24. Straits of Gibraltar 90 

25. Profile of Straits of Gibraltar 91 

26. LunarTide 96 

27. Syzygy Tide, during New Moon 97 

28. Syzygy Tide, during Full Moon 98 

29. Tide during Quadrature 99 

30. Tide at Southampton ■. 100 

31. Co-tidal Lines of British Isles 105 

32-34. Ckirves of the Tidal Waves 106 

:r>. BavofFundv 107 



Number Page 

36. Mouth of the Avon 108 

VII. Bay OF St. Michael 108 

37. Straits of Noirmoutiers 109 

38. Tides of the English Channel 110 

39. Height of the Tides 112 

40. Crossing of Tide-swellings 113 

41. Course of the Tide in Irish Sea 117 

42. Profile of a Tidal Wave 119 

43. Height of the Tidal Wave 120 

44. Plan of the Tidal Wave 120 

45. Plan of two Tidal Waves 120 

46. Tides of the Garonne 121 

47. Profile of Straits of Messina 124 

48. Lysefjord, Norway 128 

49. Fjords of Greenland 129 

50. Mouths of Cattaro 130 

51. Fjords of South America 131 

VIII. Fjords OF NoRAv AY 134 

52. Ancient Fjords of Northern Italy... . 135 

53. Fjords of South-east of Iceland....... 136 

54. Filled-up Fjords of Christiansand 137 

55. Ancient Fjords of Carentan 138 

56. Roads of the Downs 140 

57. Map of Abervrac'h 142 

58. Giants' Caldrons of Haelstolmen 143 

.^>9. Section of Giants' Caldrons 143 

60. Tidal Wells 144 

61. Clift' on the Mediterranean 148 

62. Ocean Cliff. 149 

63. Tides'of Inishmore 149 

64. Heligoland 1.52 

IX. Depths of the Zuyder Zee 154 

65. Isleof Borkum in 1738 154 

66. Isle of Borkum in 1825 155 

67. Coast between Oneglia and Savone... 157 

68. Section of Sea-shore 159 

69. Mouth of the Liamone 160 

70. Mouth of the Bidassoa 161 

71. Mouth of the Oi-ne 162 



14 



ILLUSTRATIONS. 



NUMBEE TaGB 

72. Peninsula of Giens 163 

73. Section across Peninsula of Giens... 163 

74. Peiiinsula of Cape Sepet 164 

75. Chesil Bank 165 

76. Miquelon Isles 166 

77. Coast-ridges 167 

78. Lagunes and Lidi of Venice 168 

X. Coast of North Carolina 169 

79. Coasts of Dantzic and Pillau 170 

80. Cape Ferret from 1768 to 1863 171 

81. Road of La Madeleine, California. . . 172 

82. Gulf of Carentan 173 

83. Bahr-el-Assal and Gulf of Tedjura. 176 

84. Clioa-Canzouni 183 

85. Nossi-Mitsiou 184 

86. Celebes and Gilolo 185 

87. Section of Stramboli 185 

88. Section of Panaria 186 

89. Formation of a Dune 189 

90. Formation of Sand Dunes 189 

91. Section of a Dune 191 

XL Dunes OF La Tkste 192 

92. Crescent-shaped Dunes 193 

93. Etangs, or Littoral Lakes 197 

94. Formation of Etangs 198 

95. Isle Thelenji, in Caspian Sea 199 

96. Sable Island 199 

97. Mirages at Verdon ; 211 

98. Mirages at Sea 211 

' 99. Tropical Hours of Equatorial Ocean 218 

100. Pressure of dry Air at Apenrade.... 219 

101. Variations in atmospheric Pressure. 221 

102. Oscillations of the Barometer 222 

XII. Showers of Volcanic Ashes . 228 

103. Cloud of Cinders 229 

104. Island of TeneriflFe 230 

105. Theories of Trade-winds .•. . 231 

106 Variations in Trade-winds 232 

107. Trade-winds and Monsoons 238 

108. General Direction of Winds 247 

109. Direction of Winds in Fi-ance 248 

110. Calm during Hurricane, 1861 254 

111. Calm d.uring Hurricane, 1761 255 

112. Spirals made by a Ship 258 

113. Cyclone in Indian Ocean, 1852 259 

114. Cyclone in Indian Ocean, 1860 260 

115. Parabola described by a Hurricane. 261 

116. Simultaneous Cyclones 264 

XIII. Range of Hurricane, 1848... 265 

117. Direction of Cyclones 266 

118. Tempests of the North Atlantic 269 

119. Storm in the Pyrenees 270 

120. Storm in the Pyrenees 271 



NuMBEE Page 

121. Hurricane of Monville 272 

122. Whirlwinds of Dust 274 

123. Whirlwinds of Dust 274 

124. Variations in Hygometric Degrees.. 278 

125. States of Thermometer and Hy- 

grometer 278 

126. Winds and Clouds at Teneriflfe 283 

127. Rain-fall in Valley of the Saone 287 

128. Altitudes in Valley of the Saone... . 287 

129. Comparative amounts of Rain-fall . . 289 

130. Rains around tlje Gulf of Mexico ... 293 

131. Rain-falls at Calcutta and Madras... 294 

132. Rain-fall at Anjarakandy.* 295 

133. Rain-fall in the Basin of the III 298 

134. Rains in France 299 

135. Rains in parts of Europe 299 

136. Ravines in Craters of Reunion 302 

XIV. Rain Map of the World 303 

137. Average of Stojms in Europe 806 

138. Proportion of Hailstorms 807 

139. Storms in May, 1865 308 

140. Storm in Plain North of Pyrenees... 309 

141. Hailstorms of Orleans 310 

142. Hailstorms of Lower Rhine 311 

143. Aurora Borealis of August, 1859.... 316 

144. Aurora Borealis of Sept. ,1859 317 

145. Monthly Distribution of the Aurora 318 

146. Monthly Distribution of the Aurora 819 
•147. Auroras seen at New Haven, Conn. 320 

148. Circumpolar Zone of the Aurora. . . . 321 

XV. ISOGONIC AND ISOCLINIC LiNES . 829 

149. Isodynamic Lines 330 

150. Temperatures of the Saone and 

Rhone 384 

151. Distribution of Temperatures, July. 385 

152. Distribution of Temperatures, Oct.. 336 

153. Distribution of Temperatures, Jan. . 887 

154. Valuation of Temperature at Paris . 338 

155. Continental and Oceanic Climates. . 389 

XVI. Isothermal Lines 341 

XVI. Winter Isothermal Lines... 343 

XVIII. Isothermal Lines in the 
North 347 

156. Climate of the British Isles 847 

157. Variations of Temperature at Paris. 348 

158. Monthly Variations of Temperature 849 

159. Temperatures at Brussels 350 

160. Variation of Temperature at Halle . 350 

161. Different Temperatures at Halle.... 351 

162. Succession of Climates on Mont 

■ Blanc ......'. 352 

163. Treeless Regions around North Pole 358 

XIX. Forests OF the VosGES 359 



n^LUHTBATIONS. 



15 



Number Paoe 

1G4. Forests of Transylvania 800 

165. Northward Distribution of riants... 'MVl 

166. Polar Limits of Plants 863 

167. Polar Limits of Plants 364 

XX. Sargasso Sea 369 

168. Mediterranean Flora 375 

169. Botanical Map of Java 381 

1 70. Stages of Vegetation in Teneritle . . . 38§ 

171. Stages of Vegetation on Canigou.... 382 

172. Stages of Vegetation on Sulitjelma. 384 

173. Height of Plants on Canigou and 

Alps 385 

174. Organisms from the Sea-bottom 399 

175. Profile of a Coral Reef. 423 

176. Roadstead in Island of Tahiti 424 

177. Gambler Island 425 

178. Profile of Gambler Island 426 

179. Atoll of Menchik'off. 426 

180. Brown's Archipelago 427 

181. Part of Kingsmill Group 428 

182. The Red Sea and its Coral Reefs... 429 

183. The Kfiys of Florida 430 

XXI. Great Barrier Reefs 431 

184. Bahama Archipelago 431 

185. Cross-section of Bahama Islands.... 432 

186. Eleuthira and New Providence Isl- 

ands 433 

187. Deinsity of Population in Belgium . . 443 



Number Page 

188. Density of Population in Greece.... 443 

189. Valgodemar 446 

190. Valley of the Plessur ■ 447 

191. Villages of Aliennont 458 

192. Monte San-Giulano , 459 

XXII. Grecian Archipelago 463 

XXIII. •Unexplored Polar Re- 
gions 467 

193. The Lake of Copais ' 479 

194. The Polders of Haariem 480 

195. The Zuyder Polder 483 

196. The Salt-works of Trapani 485 

197. Profile of a Sea-dike in Friesland... 487 

198. The Dikes of Uithuizen 488 

XXIV. Works at Point-de-Grave. 489 

199. The Embankments of Westkapelle. 490 

200. The Embankments of Petten 491 

201. Progressive Depths of the Clyde.... 496 

202. The Railways of Lancashire 497 

203. Populations of English Cities 498 

XXV. Passes of the Maurienne.. 499 

204. The Isthmus of Corinth 501 

XXVI. Isthmus OF Suez 502 

XVII. Isthmus of Central Amer- 
ica 503 

205. The Transatlantic Cables 506 

206. The Roadstead of Aiguillon 508 . 

207. Shipwrecks in the Mediterranean... 511 

• 



THE OCEAN; 

THE ATMOSPHERE, METEORS, AND LIFE. 



PAUT I -THE OCEAN. 

BOOK I.— THE SEAS. 



CHAPTER I. 

GENERAL CONSIDERATION'S. 

To the majoi'ity of mankind, grouped in crowded jjopulations on the 
continents, extending over scarcely a quarter of the surface of the globe, 
the sea is little else than a vast abyss Avithout limits or bottom. Even 
learned men are inclined, by an illusion of intellectual optics, to give a 
much greater geographical importance to the phenomena of continental 
regions than to those of the ocean. Just as our ancestors, beholding infi- 
nite space filled with stars and nebulse arched over their heads, imagined 
this immensity to be a dome resting on the vast structure of the earth. 

Although the influence of the ocean in the general economy of the globe 
has not been studied with the same care, relatively, as the effect of the 
rivers which flow through the plains, or of the springs which gush from 
the clefts of the hills, yet it is still of the first importance, and on it all 
the phenomena of planetary life depend, " Water is the chief of all !" ex- 
claimed Pindar, in the early days of Hellenic civilization ; and since then 
science has revealed to us that the continents themselves are elaborated 
in the bosom of the seas, and that without them earth, like a metallic sur- 
face, could give birth to no organic life whatever. Thus, as almost all the 
cosmogonies of primitive nations poetically declare, earth is "The daugh- 
ter of ocean." 

This is not simply a myth, it is a fact. The study of the strata of the 
earth — rocks, sand, clay, chalk, conglomerates — proves that the mate- 
rials of the continental masses have in great part been deposited at the 
bottom of the sea, and have assumed their form and chai'acter there. 
Many rocks, especially the granites of Scandinavia, which were formerly 
believed to have emerged in a plastic state from the interior of the earth, 
are perhaps in reality ancient sedimentary strata slowly transformed by 

2 



18 TEE OCEAN. 

mechanical and chemical action,' which operate incessantly in the great 
laboratory of the globe. Even on the sides and summits of the highest 
moimtains, now raised thousands of feet above the level of the ocean, may 
sometimes be found traces of the action of the sea in ancient times. Un- 
der our very eyes the immense work of creation, commenced by the se^s 
in the earliest ejDOch, is carried on without relaxation ; with such energy, 
in fact, that even during this short life man may witness important changes 
along their shores. If the waves undermine and slowly destroy a penin- 
sula here, elsewhere they spread out sandy beaches and form islets. New 
rocks, diifering in arrangement and apj)earance, succeed the ancient rocks 
demolished by the waves. Thus the promontories of granite are disin- 
tegrated by the action of the waters, which carry away its various con- 
stituents, quartz, feldspar, and mica, building them up into new rocks. In 
the same way the clay resulting from the slow decomposition of the por- 
phyritic or granitic feldspar is transformed into slate, which becomes sooner 
or later as hard as the ancient schists. But the dashing waves and the 
flowing rivers are not the only agents occupied in the formation of new 
rocks in the bosom of the sea. There is another ever-active agent engaged 
beneath its waters. This agent is animal life. Shells, corals, and innu- 
merable animalculse with calcareous or silicious coverings, inhabiting the 
ocean, are incessantly engaged in consuming and reproducing. They ab- 
sorb and digest matter which the rivers bring down to the sea, and secrete 
substances which form their skeletons and cases: as, generation after gen- 
eration, these swarms perish, their remains are spread out over the bottom 
of the sea or heaped up on the strand ; and at last form immense banks 
and submarine plateaux which by some subsequent elevation will be 
brought to light. 

Owing to this ceaseless renewal of the rocks, the ocean is constantly 
creating a world differing from the old one in the appearance and the dis- 
position of its beds. Thus, to the geologist, the invisible depths of the 
sea should not be of less importance than the exposed surface of the con- 
tinents. The ground which to.-day bears us and our cities will disappear, 
as the continents of former epochs have already entirely or in part disap- 
peared ; and the unknown spaces which the waters now cover will rise in 
their turn, and appear as continents, islands, or peninsulas. 

In the long period of geological centuries or ages during which the lands 
are bathed, not by the waters of the sea, but solely by the waves of the 
atmosphere, the ocean does not the less continue to modify the configura- 
tion of the globe by its clouds, its rains, and all the meteoric influences 
which take their birth at its surface. All those atmospheric agencies 
which rage about the summits of mountains, riving them and little by 
little lowering them, it is the sea which dispatches them. All those gla- 
ciers which polish the rocks, and carry down into the valleys those piled-up 
boulders, it is the clouds from the ocean which deposit them in the form 
of snow on the summits of the mountains. All those waters which pene- 
trate by fissures into the depths of the ground, which dissolve the rocks. 



THE PARENT OF WATERS. 19 

hollow out the caverns, bring mineral substances to the surface, and cause 
at times great subterranean subsidences, what are they but marine va- 
pors returning in a fluid state toward the basin from whence they arose ? 
Finally, the numerous rivers which spread life over all the globe, and with- 
out which the continents would be deserts wholly uninhabitable, are noth- 
ing else than a system of veins and veinlets, which carl*jr back to the great 
reservoir of the ocean the waters distributed over the soil by the arterial 
system of clouds and rain. It is, then, to the phenomena of this oceanic 
life we must attribute the immense geological operations of rivers, and 
the exceedingly important part which they play in the flora and fauna 
of diflerent countriesj and in the history of humanity itself The future 
discoveries of geologists and naturalists will tell us also what share in the 
production and development of those germs of vegetable and animal life, 
which reach their greatest beauty on continents, may be referred to the 
ocean. 

As for climate, upon the varieties of which all that lives upon the earth 
depends, does it not follow from movements of the ocean, asgwell as from 
the position and elevation of the masses of land ? The cold of polar lati- 
tudes would be more rigorous, and the heat of the tropics more intense, 
and these extremes would undoubtedly destroy most of the beings now in 
existence, if the currents of the ocean did not convey water from the poles 
to the equator, and from the equator to the poles ; thus constantly tend- 
ing to an equalization of temperature. In the same way the atmosphere 
of continents would be completely deprived of vapor, and so perhaps ren- 
dered unfit for breathing, if the humidity it derives from the sea were not 
spread by the winds all over the globe. Thus the ocean blends the con- 
trasts of climate, and makes a harmonious whole of all the distinct regions 
of our planet ; it awakens and preserves life on the earth, which it has de- 
posited layer by layer, which it waters by its vapors, and renders fertile 
by its springs and its rivers. 



20 THE OCEAN. 



^ CHAPTER II. 

OCEANIC BASINS. — DEPTH OP THE SEAS. — LEVEL OF THE SURFACE OF THE 

OCEAN. 

The seas which cover the greater part of this planetary sphere have 
not comjDletely inclosed basins. They all have their origin in the great 
common reservoir of the Antarctic Ocean, and cornmunicate with each 
other by wide straits, or by sheets of water of secondary importance. 
This partial absence of boundaries, and their enormous extent of surface, 
deprive the seas of that harmony of form observable in the continental 
masses. Yet, wherever the water washes the shores of the land, it neces- 
, sarily reproduces its contour ; and, in consequence, the sea everywhere 
presents a distribution exactly the opposite of that of the earth. The 
twofold basin of the Atlantic, with its wide central expansion, corre- 
sponds to the two continents of America, with their narrow uniting isth- 
mus. The Pacific itself is divided by its immense Archipelago into two 
vast distinct seas ; and the Indian Ocean in the south balances the mass 
of Asia in the north. While limiting with its waves the shores of the 
land, the ocean penetrates far into the interior, either by large rounded 
gulfs like those of Guinea and Bengal, or by seas bordered with chains of 
islands and islets, like the China Sea and that of the Antilles, or by an in- 
tricate net-work of channels like those of Sunda, and the Polar Archipela- 
go of America. Certain seas also are almost completely inclosed, and 
communicate with the remainder of the ocean onl}'- by narrow outlets, as 
is the case with the Mediterranean and the Red Sea. 

The bottom of all these seas is not always horizontal or even regularly 
inclined. It is certain that the bed of the sea has, like our continents, 
but in a far less degree, plateaux, valleys, and plains. Geology reveals 
to us that in the course of ages, the highlands of the continents sink be- 
neath the oceanic expanses, and the abysses formerly hidden by their 
waters emerge to the light and reveal the inequalities of their surface. 
Were not the plains and the hills, which now bear our cities and our har- 
vests, in past ages covered by the waters of the deep ? Do we not see 
on the flanks of the Himalayas, 18,000 feet above the level of the mouth 
of the Ganges, shells which the sea has there deposited in the strata ? 
And do not our navigators search the bottom of the ocean, and, so to 
speak, investigate its inequalities with those enormous " feelers," their 
sounding apparatus ? 

We may well imagine that the submarine surface still preserves all its 
primitive rudeness ; and that its rocks, cliffs, and fells uniformly present 
edges unworn and sharp, the marks of fracture, just as on the day when 
the solid rock was first cleft. And, in fact, in the depths of the sea there 



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SUDDEN CHANGES OF DEPTH. 21 

are no frosts to break off projecting peaks, no lightnings to split, no gla- 
ciers to carry them or crumble them away, no meteoric influences to cor- 
rode and round them. Nevertheless, if there are not in the sea, as on 
the land, agencies like these, ceaselessly at work leveling projections, 
there a»e others which as ceaselessly labor to smooth the asperities of 
the surface. There are the sedimentary dej^osits brought down by the 
rivers, and innumerable millions of the skeletons of animalcula3, which live 
in the deep, or fall like snow from the upper strata of the water and 
gradually fill up the submarine valleys. Those fantastic mountain chains 
drawn on the bed of the sea by Buache and other geographers can not, 
therefore, really exist, since the geological agencies at work under water 
differ from those which carve out the table-lands and mountains on our 
continents. If some immense eddy prevented the particles from being- 
deposited in the deep parts of the ocean, then the rocks and the rifts of 
the abysses Avould keep their first form, like those peaks and craters of 
the moon which are not worn away by the inclemencies of an atmosphei'e. 
There are, indeed, tracts in thq sea where, perhaps from the influence of 
a submarine counter-cuiTcnt, the rocks of the bottom are not covered by 
organic alluvium. In the deepest part of that great arm of the sea which 
separates the Faroe Islands from Great Britain, Wallich drew up from a 
depth of more than 600 fathoms* a large fragment of quartz detached 
fronPthe living rock, and several pieces of basalt; it is quite possible, 
however, that these fragments had been dropped there by an iceberg. 

In general, the sea-bed extends for wide spaces in long undulations and 
gentle slopes. Sailors, who are carried swiftly over the water by wind 
or steam, and who generally take soundings at places far distant from one 
another, are tempted to exaggerate the magnitude of inequalities in the 
sea-bed, and to see chasms and precipices, where the declivity is in reality 
inconsiderable. Escarpments, similar to those of the continental mount- 
ains, very rarely present themselves; Fitzroy was greatly surprised to 
find in the neighborhood of the Abrolhos, near Brazil, such rapid slopes, 
that the lead on one side of the shij? indicated from 4 to 6 fathoms only, 
while on the other side it marked from 16 to 22 fathoms. Sometimes a 
special cause explains these abrupt changes of the level. Thus M. de 
Villeneuve-Flayosc discovered in the Gulf of Cannes, a spring of fresh 
water springing from the depths of a kind of well, the sides of which 
sloped at an angle of 27 degrees. But how can we explain that singular 
gulf which extends immediately in front of Cape Breton, on the coast of 
the Landes ? Ought we to attribute its formation to the meeting of the 
tides, which takes place in the channel of the Gulf of Gascony? This is 
a question which it is not yet possible to decide. 

We can form some notion of the submarine tracts by surveying the 
countries that have emerged from under water at a comparatively recent 
epoch. The Landes of France, the low lands which have replaced the 

* Marine soundings are always taken in fathoms ; a fathom is equivalent to 2 yards, or 6 
feet linear. 



22 



THE OCEAN. 







, KXauu Breton" 



Depths under Sfath. 

Depths from Bfath. to 54 fath. 



Depths of more than 54 fath. 



Fig. 1. Gulf of Cape Breton. 



Gulf of Poitou, a great part of the Sahara, the pampas of La Plata, fur- 
nish remarkable examples of the regularity of inclination which generally 
characterizes the bottom of the sea. Even rocky coasts, like those of 
Scotland and Scandinavia, have been leveled here and there in their lower 
parts, that were not long ago covered by the waters of the Atlantic. If 
earthquakes and fissures of the soil, volcanoes and slow oscillations of the 
terrestrial crust, did not on their side increase the inequalities of our 
planet's surface, it is certain that the incessant contribution of fluvial de- 
posits, the fragments of rocks worn away by the waves, and, above all, 
those remains of swarming organisms which fill the sea, would have ef- 
fected, as an inevitable result, the equalization of the ocean-beds, and the 
transformation of their abysses into scarcely indicated slopes; the waters, 
on their side, would gradually invade the surface of the continents, till, 
after the operations of myriads of centuries, the earth would become 
again what it formerly was, a spheroid with its surface entirely covered 
by a bed of water of uniform thickness. 

According to an ancient popular opinion, which, in default of direct 
observation, was not more contradictory to good sense than many other 
hypotheses called scientific, the sea was " bottomless ;" and this prover- 
bial expression is still that which best conveys to many ignorant persons 
the real state of things. At the commencement of last century Marsigli 
himself spoke of "the abyss" of the Mediterranean as of a gulf absolutely 
unfathomable.* On the other side, mathematicians, supported by theo- 
* Histoire de la Mer, p. 10. 



ESTIMATED DEPTH OF THE SEA. 23 

retical considerations, have attempted to estimate by calculation the av- 
erage d'epth of the seas. Butibn, who does not quote the Italian author 
from whom he has borrowed his argument, gave to the ocean a deptli of 
water equal to 230 toises, or 240 fathoms.* The astronomer Lacaille, 
whose estimates are no nearer those that recent soundings have rendered 
probable, allowed from 164 to 273 fathoms of depth to the sea. Laplace, 
who erroneously estimated the mean elevation of the land at 3280 feet 
(that is to say, three times the height now approximately determined),! 
thought that the waters of the sea must also be of about equal depth. 
Young, drawing his deductions from the theory of the tides, assigned 
about 2735 fathoms to the waters of the Atlantic, and from about 3250 
to 3800 fathoms to those of the South Sea. Arnold Guyot remarked that 
this depth assigned to the Atlantic would be, in fact, that of the trench 
formed in this marine valley, between the coasts of South America and 
Africa, having the plateaux of Bolivia on the one hand, and those of the 
Lupata Mountains on the other. J This last estimate has, however, only 
a relative value : if we aj^ply it to the Pacific, continuing westward and 
eastward the coasts of Asia and America, we should find as the lowest 
point, and lying (according to this hypothesis) to the east of Easter Isl- 
and, a depth of about \5^ miles — three times the elevation of the highest 
mountain in the world. Evidently it is by direct observation that we 
must hope some day to know all the projections and undulations of the 
bottom of the ocean ; but the instruments which seamen can command 
are still imperfect, and, except for inconsiderable depths, do not give re- 
salts of rigorous accuracy. In those latitudes where the water is many 
hundreds, or even thousands of fathoms in depth, they can not risk the 
taking a sounding unless the atmosphere and the waves are in an excep- 
tional state of tranquillity ; and even then the slenderness of the cord, 
the weight of the apparatus, the enormous pressure it endures as it de- 
scends, and which increases at the rate of one atmosphere for every elev- 
en yards of immersion, and finally, the long hours which must be em- 
ployed in this delicate operation, greatly endanger the final success. 
Unless instruments furnished with electrical bells, like those of Schneider 
or of Gareis and Becker,§ and others more easily employed, more rapid 
and sure, are used, " bathymetric " observations will be always at great 
distances from each other, and it will not be possible to construct a sub- 
marine map in relief, such as is being constructed of the surface of the 
continents. Besides, it is very rarely that sailors take soundings in the 
deep seas simply for the scientific pleasure of investigating the depth of 
the ocean. It is solely for the requirements of navigation, of commerce, 
and of industry, that they have observed the depth of the sea, either in 
gulfs like the Adriatic, or in parts that are filled with sand-banks like the 
North Sea, in the neighborhood of coasts and rocks laid down in ancient 

* Theorie de la Terre : les Fleuves. 

t Humboldt. See the section entitled Harmonies and Contrasts. 

X Earth and Man, pp. 76, 77. § Physiographie des Meeres, 1867. 



24 



THE OCEAN. 




Fig. 2 —Depths of the Adriatic. 
(The parts marked by cross-shading are 270 fathoms and upward in depth.) 

maps, or in those parts of the ocean which are destined to receive elec- 
tric cables. In the open sea ships sail almost entirely over nnmeasured 
depths. 

Owing to its elongated form, and to the amphitheatre of lofty monnt- 
ains which all but wholly surround it, the Adriatic offers a very remark- 
able example of the continuation of the continental slopes below the level 
of the sea. The bed of the northern part of this gulf, which is a continu- 
ation under water of the level plains of Venetia, has an exceedingly gen- 
tle slope, much less, in fact, than that of the plains of Lombardy, which 
seem horizontal.* The sounding-lead shows only a depth of 54 fathoms 
beyond the narrows formed by the islands of Zara and the headland of 
Ancoua ; thus more than a third of the Adriatic is found not to exceed in 
* G. Collegno, Geologia deW Italia, p. 12. 



THE ADRIATIC AND THE MEDITERRANEAN. 25 

• 
mean depth rivers like the Mississippi and the Amazons. Farther south 

the submarine declivity, which continues on one side that of the Apen- 
nines, on the other that of the Alps of Dalinatia, becomes comparatively- 
greater, and the sounding-lead descends to about 110 and even 170 fath- 
oms below the surface. At this spot the sea forms a sort of hollow, 
bounded on the south by a submarine isthmus uniting the peninsula of 
Manfredonia with the isolated rock of Pelagosa, and with the islands of 
the Dalmatian coast, Lagosta, Curzola, and Lesiua. Beyond this isth- 
mus, and extending as far as the Straits of Otranto, is another and much 
deeper hollow, toward the middle of which the soundings indicate a depth 
of nearly 500 fathoms ; and on the east rise the precipices of Montenegro, 
the roots of which descend very rapidly beneath the waters. Thus the 
soundings of the Adriatic confirm the observations, made long ago by 
Dampier and many other navigators, that the sea is generally deep at the 
base of abru2Jtly sloping mountains, and, on the other hand, that there is 
but a slight depth of water near low coasts. 



1 


t 








XT) 

a- 


X df 31 d. 


t 

00 
03 


o 


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Fig. 3.— Profile of the Bed of the Adriatic. 

As to the Mediten-anean properly so called, it is almost unknown, ex- 
cept in those parts which have been explored for the laying of telegraphic 
cables ; however, on comparing with one another all the soundings, and 
the various tracks followed by those who have laid the wires, we can at 
least form a general notion of its submarine surface. If the waters of the 
Mediterranean were suddenly lowered about 110 fathoms, it would be di-. 
vided into three distinct sheets of water : Italy would be joined to Sicily, 
Sicily would be united by an isthmus to Africa, the Dardanelles and the 
Bosporus would be closed, but the outlet of Gibraltar would remain in 
free communication with the Atlantic Ocean. If the level was loAvered 
by about 550 fathoms, the ^gean, the Euxine, and the Adriatic would 
wholly disappear, or only leave in their beds unimportant pools ; the re- 
mainder of the Mediterranean would be divided into several seas like the 
Caspian, either isolated or communicating with each other by narrow 
channels, and the terminal promontory of Europe would be joined by the 
isthmus of Gibraltar to the mountains of Africa. A depression of about 
1100 fathoms would leave nothing but three inland lakes; to the west a 



26 TEE OCEAN. 

• 

triangular basin occupying the centre of the depression between France 
and Algeria ; in the middle, a long cavity extending from Crete to Sicily ; 
and eastward, a hollow lying in front of the Egyptian coast. The great- 
est depth of the Mediterranean, exceeding 2200 fathoms, lies to the north 
of the Syrtes, almost in the geometrical centre of the basin.* 

It is the same with the North Atlantic Ocean as with the Mediterra- 
nean. The depth of the central valley, extending from north to south be- 
tween Europe and the New World, is only known in a general manner. 
But the gulfs and straits which project from the ocean between the north- 
ern countries of Europe, such as the Channel, the North Sea, the Categat,' 
the Baltic, have been almost completely exploited by the sounding-lead. 

The North Sea in all its northern part, from the 51st to the 57th degree 
of latitude, presents a mean depth of only about 16 to 27 fathoms, except 
near Newcastle-upon-Tyne, where the bottom is found to be from about 
49 to 65 fathoms below the surface. Vast tracts of sand and mud — the 
White bank, the Black bank, the Brown bank, the Dogger bank, the 
Fisher bank — separated from one another by fosses and lateral channels, 
deejDer by from about 6 to 11 fathoms, almost entirely fill its bed, and 
stretch as far north as the Shetland Islands. There, as in the centre of a 
whirlpool, is dej)osited the marine alluvium, while that arm of the ocean 
follows the precipitous shores of Scandinavia over the rocks and compact 
clays of the bottom. In these parts the lead descends to about 164 and 

Scotland ... F Norway 

g:il:t?:tl:tit:l: I; it; t I: l" I: I: t. 1 1 &: 




Fig. 4.— Profile of the Bed of the North Sea, from the north point of Scotland to Stavanger, in Norway. 

even 437 fathoms from the surface of the sea; and in the centre of the 
Skagerrack, between the sandy beach of Jutland and the bold shores of 
Norway, nearly 443 fathoms have been reached. One seems to see here, 
in vaster proportions, a repetition of those narrow and deep trenches which 
surround isolated rocks left standing out on flat sandy shores. 

From the Skaggerrack to the Categat, which may be considered as the 
submarine threshold of the inland waters of the Baltic, the transition is 
effected somewhat abruptly. The Categat presents nowhere more than 
93 fathoms, the mean depth of its channel is only 64 fathoms, and the 
banks of sand and mud render its navigation difficult. The depth of 
water is reduced to 16, 11, and even in some places to 5 fathoms, in the 
Sound and the Great Belt, which form the entrances to the Baltic Sea, 
properly so called. This vast reservoir, which partakes at the same time 
of the nature of a gulf by its free communication with the ocean, and of 
* Bottger, das Mittelmeer ; Mittheilungen von Petermann, 1866. 



The OceaTi.&c SUBMARINE PLATEAU OF THE BRITISH ISLES. jr^ n. 




Rn^av^d by EfKard . 



y%e ttnts irniictit^ the d< ffereni ricplhs in. feet 



Bra-v™liT-AVuai<>Triii 



I I 

S6. 



DEPTHS OF TEE ENGLISH CHANNEL. 



11 




J)i^i7vs Tnore^ t/aiur Si-yiUTv' 



I I Depths under' S^/oI/l.. 

Fig. 5.— Depths of the English Channel. 

an inland lake by the slight saltness of its waters, has a mean depth of 
22 to 33 fathoms, analogous to that of the Categat. According to Foss, 
the greatest depth (between the island of Gothland and Esthonia) would 
be found at only 98 fathoms below the surface of the sea ; but, according 
to Anton von Etzel, the lead would not reach the bottom at less than 150 
fathoms in the deepest hollow. 

To the south-west, the North Sea communicates by the Straits of Do- 
ver with the Channel — a narrow arm of the sea which may be considered 
as a mere accident of the earth's surface, as a kind of maritime trench, so 
inconsiderable is its depth compared with that of the ocean. In order to 
form a true notion of the depth of the Channel, compared with its Avidth, 
one must imagine a miniature of this sea drawn on a scale of one yard for 
two-thirds of a mile, on a perfectly horizontal surface. This sheet of wa- 




Fig. 6 Profile following the Line of the greatest Depth, 

ter would not have less than 547 yards of length, and its width would 
vary, according to the coast-lines, between 36 and 240 yards. And yet, 
notwithstanding this considerable surface, the greatest depth would be 
less than 2 inches at the entrance. In the deepest hollow of the Chan- 
nel, between the hillock representing Start Point and that of the Sept- 



28 



THE OCEAN. 



lies, it would be less than 2J inches. A siDarrow could hop this minia- 
ture sea.* We see that it is as easy to exaggerate the importance of 
the depth of the sea as it is the height of mountains. The section an- 
nexed to Plate I. shows the proportionate depth of water between the 
shores of Dover and Calais. 

On leaving the Channel, the parts of the oceanic bed which have been 
explored by sounding are more and more distant toward the west, and 
then become quite rare. Finally, many hundred miles out at sea, where 
the true abysses commence, soundings have been only taken at intervals 
of about 30 and even 55 miles apart. The points thus marked, which 
have served for drawing the submarine chart of the North Atlantic, are 
therefore by no means numerous, but nevertheless we have in it a pretty 
exact representation of the relief of the ocean-bed. The average depth 
of Avater which separates the coasts of North America and those of Eu- 
rope is about 1915 fathoms, but the central valley presents a surface rel- 
atively uniform, and much less varied than that of Europe or even the 
United States ; the greatest slopes do not probably exceed those of the 
river-beds which seem nearly horizontal; and it may be said- that the 
depth of the sea is concentric with the surface. Hence the name of " the 
telegraph plateau," given by Maury to these plains some time before the 
first transatlantic cable was laid. The most considerable depth of this 
plateau is 4846 yards^— that is to say, about one-sixteen hundred and 
thirty-ninth of the width of this ocean ; this being a thickness relatively 
less than that of the finest needle.f The section on Plate III. enables us 
to compai'e the relief of the continental surface and that of the oceanic 
depths from the coasts of the United States to those of Europe. It is 
true that, in order to render the vertical dimensions visible, it has been 



t^ 



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^^ 



60° 50* 



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30^ %t 



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Fig. 7.— Section of the Atlantic in the Tropics. 

necessary to exaggerate them in the enormous proportion of twenty- 
fold. To the south the depth of the sea becomes more and more varied. 
An imaginary section from the plateau of Anahuac to Senegambia, across 

* Saxby, Nautical Magazine, March, 1864. 

t Bischof, die Gestalt der Erde und der Meeresflache, p. 6, and following (note). 



Tie Ocean. &c. 



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IS. NEW" YORK 



DEPTH OF THE ATLANTIC. 29 

Yucatan, the Caribbean Sea, the Antilles, and the central basin of the 
tropical Atlantic, presents a much more unequal surface than that of the 
telegraphic plateau ; but the true oceanic part of the basin equally shows 
a great uniformity in almost its entire extent. 

Considered as a whole, the North Atlantic is a depression whose sides 
descend gradually toward a central hollow situated between the coasts 
of the United States, the Bermudas, and the Banks of Newfoundland. A 
fall of the waters of less than 110 fathoms would reveal the submarine 
groundwork upon which France, Spain, and the British Isles rest. This 
is, indeed, the true foundation of the European continent, for immediately 
beyond this basement, which forms the extreme angle of the Old World, 
the bei of the sea, at an inclination of about eight degrees, descends 
gradually from 110 fathoms to 1640 and 2187 fathoms below the waves. 
A fall in its level of 1094 fathoms would diminish the width of the Atlan- 
tic more than half, would leave the Gulf of Mexico completely dry, and 
only leave an elongated lake in the central part of the Caribbean Sea. 
If the present level were lowered by 2187 fathoms, a continent separated 
from Europe and America by two narrow channels, and extending over 
a space of from about 1550 to 186(> miles, would stretch into the torrid 
zone, and, by a remarkable coincidence, would affect that peninsular con- 
formation and southerly direction presented by Greenland, Scandinavia, 
Spain, Italy, Greece, Arabia, India, and the three great continents of the 
South.* A lowering of 3280 fathoms would completely unite Newfound- 
laud to Ireland, and consequently form a bridge between the Old and 
New Worlds. Even of the central Atlantic there would only remain a 
narrow "Mediterranean" sea in front of the, Antilles and Guiana. Final- 
ly, let the waters be lowered by 4375 fathoms, and the northern part of 
the Atlantic would be reduced to a small triangular " Caspian," situated 
between the Azores, the Banks of Newfoundland, and the Bermudas. 

In the present state of science, it is impossible to draw an approximate 
chart of the depths of the South Atlantic similar to that which one can 
construct of the bottom of the northern part. It even appears that many 
of the soundings made in this part of the ocean must be considered null, 
because the explorers have not taken into account the deflection of the 
sounding-line occasioned by submarine currents. The depth of 7600 fath- 
oms obtained by Captain Denham, R.N., is accepted by M. Bischof and 
other geologists with all confidence, because this explorer took care to 
raise the cord several times by a hundred yards, and when thrown again 
it always stopped at the same point. As to the sounding of 8695 fath- 
oms, announced by the American Parker, it is certainly erroneous, since 
later, in the same latitudes, they have found the bottom at 3007 fathoms 
only. Not knowing the depth of water in the different parts of the South 
Atlantic, mathematicians have tried at least to calculate the mean depth 
of the entire basin by the swiftness of the translation of the tidal waves. 
They have estimated the mean force of the bed of water ia the Atlantic 

* Sir John Herschel, Physical Geography, p. 35. 



30 THE OCEAN. 

Ocean from the SOtli degree south to the 50th degree north latitude to be 
about 7330 yards. Now, the mean depth of the north basin being very 
nearly 2187 fathoms, the depth of the southern basin must be estimated, 
according to this calculation, at about 4920 fathoms.* However, these 
figures rest on the very contestable and much contested hypothesis that 
the tides, instead of forming in a distinct manner in every basin of the 
ocean, have a common origin in the great South Polar Sea, and roll toward 
the north like one immense wave, in the double valley of the Atlantic.f 

As to that part of the Pacific Ocean comprised between Japan and the 
coasts of California, it is not by the swiftness of the proj^agation of the 
tides, but by that of the earthquake-waves, that the mean depth may be 
approximately estimated. In the terrible earthquake of Decemlter 23d, 
1854, which j)artially destroyed several Japanese towns, among others 
Yeddo and Simoda, the vibrations of the marine surface traversed an 
oceanic space of 6842 miles in twelve hours and a few minutes ; and Prof 
Franklin Bache was able to calculate, in consequence, the swiftness of the 
waves and the depth of the ocean across which they were propagated : 
this depth is an average of 2342 fathoms.J Besides, various authentic 
soundings taken in the northern basfci of the Pacific between California 
and the Sandwich Islands confirm the result of this calculation, since they 
indicate a depth varying from 1968 to 2570 fathoms. Not far from the 
coast of California 2700 fathoms of depth have been found. § Between 
the Philippine and the Marianne Islands two other soundings have given 
3267 and 3609 fathoms, and even in this last operation the lead has 
brought up specimens of the submarine soil, and 117 species of minute 
forms of life. Finally, between the Pacific and the Indian Sea, to the 
south of the East India Islands, Captain Ringgold found the bottom more 
than 8f miles below the sui-face. Thus one might throw into this abyss 
of the sea not only Pelion on Ossa, but Gaourisankar itself, the highest 
mountain of the globe ; and even if on its peak Mont Blanc were set up, 
the summit of this colossus of the continent of Europe would not reach 
to the surface of the water. 

The Indian Ocean, too, is probably very deep in the greater part of its 
extent, but we only know those j^arts nearest land, and those in hardly 
moi'e than an approximate manner. Its gulfs, like those of the Mediter- 
ranean and the Atlantic Ocean, have relatively a slight depth of water : 
the Persian Gulf, for instance, having a mean depth of only 54, and the 
Red Sea of 163 to 273 fathoms. Those parts of the Gulf of Bengal which 
are adjacent to the Coromandel Coast and the delta of the Ganges in- 
crease only very gradually in depth, except near the northern extremity 
of the Gulf, where a prodigious abyss has been discovered, called " the 
Great Swatch," which is no less than 2187 fathoms deep, and is bounded 

* Sir John Herschel, Physical Geographj, p. 72. 
t See below, the section entitled The Tides. 
% Report of the United States Coast Survey. 
§ Sir John Herschel, Physical Geography, p. 39. 



DEPTH OF THE ANTARCTIC SEA. 



31 



oil the north, east, and west by deposits of mud and ooze, which the lead 
touches at some five or ten fiithoras. The formation of this singular fun- 
nel is perhaps due to an eddy of tidal waters, commencing precisely at 
that spot where the alluvium of the Ganges is brought down to mingle 
with the sea.* 

Almost all the Indian Archipelago, Sumatra, Java, Borneo, and the ad- 
jacent, islands, rest on a submarine bank, having on an average only a 
depth of 33 fathoms, and even at the deepest places only 55 fathoms. 
This is probably the base of an ancient continent, of which the innumera- 
ble islands scattered over the sea in these latitudes are the remains. An- 




Fig. S.— Depths of the Sea at the mouth of the Ganges.t 

Other bank, extending for 435 miles to the north and north-west of Aus- 
tralia, suppoi'ts that continent, and all the neighboring islands, including 
New Guinea. A channel of very deep water, not yet sounded, separates 
from the Asiatic archipelago those higher Australian levels which also 
seem to be only the ancient fragments of vanished lands.J It is around 
these two great continental basements that the Pacific and the Indian 
Oceans, properly so called, commence. 

With respect to Antarctic latitudes, 1722 fathoms have been found be- 
tween the 63d and 64th degrees : near the VSth degree, at the very side 
of the enormous barrier of ice, which hinders any advance toward the 
pole. Sir James Ross has touched the bottom at 415 fathoms. And this" 
is all the information which navigators have given us." The icy sea of 
the north is better known, at least in some parts. To the north of Sibe- 

* See the section entitled Rivers. 

t The part marked by cross-sliading represents the " Great Swatch." 

i See below, the section entitled Shores and Islands, and The Earth and its Fauna. 



32 THE OCEAN. 

ria, the bed of the sea, continuing the slope of the hardly-inclined " tun- 
dras,^'' extends toward the pole with such a slight declivity, that at 156 
miles from the coast the lead only shows a mean of from 14 to 15 fath- 
oms. Around Spitzbergen and the western shores of Scandinavia the sea 
is much deeper, and on the precipitous coast of Norway its abysses join 
the deep channel which separates Scandinavia from the lesser depths of 
the North Sea. More to the west, between Scotland and Iceland, the 
parts explored by McClintock, with the view of laying the telegraphic 
cable, are rarely more than 328 fathoms, and nowhere present a depth 
of water of more than 670 fathoms. Between Iceland and Greenland a 
depth of 1547 fathoms has been sounded, and in Baffin's Straits are abyss- 
es of nearly 2000 fathoms. This great depression makes Greenland a 
country quite distinct from the American continent. The plateau upon 
which this grand island rests presents slopes relatively very steep. On 
the western side the declivity is in certain places one yard for every five 
of distance, while the western slopes of the submarine plateau of Ireland, 
which are among the most rapid in all the ocean, have about one yard 
of fall for every eight yards of length.* 

We can see clearly that the state of our knowledge of the subterranean 
surface is still very limited; yet the sum of the facts which have been 
already scientifically confirmed gives a great probability to the opinion, 
very natural on other grounds, that the oceans deepen gradually toward 
the south, where the waters occupy the greatest extent on our planet. 
The celebrated chemist and geologist, Bischof, thinks we may conclude, 
from the comparison of all the soundings, that the bottom of the sea is on 
an average as near the centre of the globe as the poles themselves. In 
certain latitudes, and notably toward the VSth degree north, the terres- 
trial radius drawn to the bottom of the sea is even less than that at the 
pole, which perhaps is to be attributed to the wearing away of the soil 
by icebergs. But, on the other hand, in the greater part of the ocean the 
bottom of the sea is a little more distant from the centre than the poles, 
which doubtless arises from the alluvium brought down by the rivers and 
the accumulations of organic remains. Thus the part of the globe cov- 
ered by the seas might be considered as perfectly round, and Newton's 
hypothesis, explaining the bulging at the equator by the state of fluid- 
ity in which the planetary mass had originally been, would become un- 
necessary.! 

As to the mean depth of the whole mass of the marine waters, we can 
hardly estimate it at less than about three miles ; since, as we have 
already seen, the entire basin of the Atlantic, and that of the Northern 
Pacific, which border upon the great northern continents, are deeper by 
many hundreds or even thousands of fathoms. 

Taking as the total surface of the ocean an extent of more than 145 
millions of square miles, we find that the sea forms a volume of about 2^ 

* Wallich, North Atlantic Sea-bed, p. 18. 
t Gestalt der Erde und der Meeresfldche. 



DISTURBANCES OF THE SEA-LEVEL. 33 

million billions of cubic yards, that, is to say, the 560th part of the planet 
itself. Sir John Herschel* gives much higher figures for the same volume 
of Avater ; but he has taken, as the basis of his calculation, the probable 
maximum of the depth of the seas, that is to say, four English miles, more 
than 3738 fathoms. We can not speak yet with certainty, but one day, 
thanks to the new observations which are added every year to those 
which science already possesses, it will be possible to give figures more 
relatively exact for the depth of the marine abysses, and the mass of wa- 
ter that fills them. One thing is certain, that the highest jjart of the 
continent raised above the surface of the waters is of much less elevation 
than the depth of the sea; and we can estimate the land above the level 
of the sea at only about a fortieth part of the mass of waters. Besides 
which, the land itself contains within it an enormous quantity of water 
united either chemically or mechanically with all rocks. 

The water of the seas, urgied by the force of gravitation, constantly 
seeks its level, like the water of rivers and lakes. When, in consequence 
of very rapid evaporation, or of a succession of tempests blowing from 
the same quarter of the horizon, the surface of the sea is lowered in any 
gulf, the waters from the adjacent parts rush toward the impoverished 
space, to fill the void. In the same way, when great rains, the swelling 
of large rivers, or the action of winds have raised the level of the sea in 
one point, this local swelling soon subsides, and its superfluity is dis- 
persed over the surrounding surfaces. We may, therefore, consider the 
mean height of the sea as the same in eveVy ocean, since the natural 
movement of water tends ever to re-establish an equality of surface in all 
parts where an accidental disturbance has occurred. 

Nevertheless, the diversity of climates, of winds, and of currents, is 
such, that certain seas, separated from one another by a narrow isthmus, 
present permanently unequal levels. Thus several German engineers be- 
lieve that they have established the fact that the Baltic Sea, into which a 
great numb^er of considerable rivers discharge themselves, is on an aver- 
age some inches higher (?) than the North Sea.f In the same manner the 
Atlantic, whose waters spread out on one side into the North Sea, and on 
the other into the Mediterranean, would have a mean level scarcely high- 
er than that of the two basins which it supplies ; while the Black Sea 
and the Gulf of Venice, receiving, like the Baltic, several large rivers, 
would, like the latter, be proportionably elevated. On the two sides of 
the Isthmus of Suez the waters are also found at slightly unequal heights. 
According to the engineer I^urdaloue, the mean level of the Red Sea at 
Suez exceeds by 31^ inches that of the Mediterranean near Port Said ; at 
low tides the two sheets of water are perceptibly of the same level, while 
at high-water the sea is sometimes higher by 3^^ feet in the Bay of Suez 
than at the northern extremity of the maritime canal. A similar differ- 
ence, too, occurs between the Bay of Colon and the Gulf of Panama, and 

* Physical Geography, p. 17. 

t Woltmann ; Von Hoft', Verdnderungen der Erdoherfldche, t. iii., p. 328. 

3 



34 , THE OCEAN. 

there also it is the mass of wat«r in which the tides have the fullest 
swell, that is to say, the Pacific Ocean, which has the highest level. But 
the measurements made on the always unstable level of the sea are very 
delicate operations, as one can so easily make a mistake at starting, 
through the oscillations of the ebb and flow ; and over spaces of many 
miles, divided by various obstacles, it is very difficult to avoid slight er- 
rors. At all events, it is certain that the surface of the sea, unceasingly 
traversed and perturbed by winds, currents, and tides, is not perfectly 
horizontal at any point of the globe. 



SALTNESS OF THE SEA. 35 



CHAPTER m. 

COMPOSITION OF SEA-WATER.— SPECIFIC WEIGHT. — SALT MARSHES, NATURAL 
AND ARTIFICIAL. — VARIOUS SUBSTANCES, — DIFFERENCES OP SALTNESS. — 
MARINE SALT. 

Besides the ooze, the remains of animalculae, and innumerable frag- 
ments held in suspension, the sea-water is also charged with chemical 
substances ii^ solution, which give it a specific gravity considerably su- 
perior to that of fresh water. This varies in all seas, according to the 
quantity of the substances dissolved, the amount of evaporation, the con- 
tributions of rain and rivers, the direction of the currents and counter- 
currents. In the polar seas the specific gravity of the waters is also 
modified by the formation, or melting, of the ice. Every variation of 
temperature, every local movement of the sea, causes a more or less per- 
ceptible modification in the proportion of the salts dissolved, and in the 
specific gravity of the water. Thus we can only obtain an average for 
the various conditions of the fluid mass in the diSerent seas. 

The mean specific gravity of oceans with deep basins is nearly 1028 ; 
that is to say, sea-water weighs 2 '8 per cent, more than the same bulk of 
distilled water. In the Mediterranean, where the heat of the sun evap- 
orates more water than the rivers bring down to it, the average specific 
gravity exceeds, 1029; in the Black Sea, on the other hand, where very 
considerable rivers of fresh water discharge themselves, the specific grav- 
ity is reduced to 1016. And all the intermediate degrees between these 
exti'cme specific gravities are found, according to the varied physical 
conditions which exist, in other seas. Furthermore, it seems to be estab- 
lished that the waters of the ocean in the southern hemisphere are, on an 
average, lighter than those of the northern hemisphere,* 

The average quantity of all the salts contained in the sea, or the salt- 
ness of sea-water, was estimated by Bibra and Bischof at 35*27 parts in 
1000 ; but much more complete observations made since by Forchham- 
mer have reduced this i^roportion to 34'40. Besides, almost all the analy- 
ses, which up to the present time have been made of sea-water, confirm 
the general opinion of chemists, that the relative proportion of the mat- 
ters dissolved is the same in all seas. The quantity of common salt (chlo- 
ride of sodium) dissolved in sea-water is always a little more than three- 
(]uarters (75*786) of the total mineral matter held in solution. 

In the north tropical Atlantic, on the coasts of the Sahara and of Mo- 
rocco, where the sea receives no tributaries, and where, on the other 
hand, the evaporation is very rapid, the average of oceanic salts is nearly 
38 parts in 1000. In mid-ocean, and more especially in the neighborhood 
* Homer ; J. Davy. — Bischof, Lehrbtich der chemischen Geologic. 



36 



THE OCEAN. 



of America, where the water of many great rivers mingles with that of 
the sea, the saltness is less by one, two, and even three thousandths ; but 
it is generally greater in the tepid waters of the great current called the 
Gulf Stream, which crosses the Atlantic obliquely. The proportion of 
salts contained in this current always exceeds 35 thousandths,* while the 
water that flows from the pole toward the equator by Baffin's Bay con- 
tains only about 33 thousandths. It is to the enormous accumulation of 
ice that these currents owe the slightly less saltness of their waters. 
The quantity of cold water which flows from the Antarctic Pole toward 
the south of Africa and America contains likewise less saline matter 
than the seas of the temperate and equatorial zones. 




Fig. 9.— Comparative Saltness of Seas. 

With regard to basins almost inclosed, like the Mediterranean, the Ca- 
ribbean Sea, and the Baltic, the saltness ought evidently to be greater or 
less there than in the ocean, according as the evaporation is in excess of 
or is inferior to the fresh water brought by the rivers and the clouds. In 
the Mediterranean, the loss in evaporation being more considerable than 
the contributions of fresh water, the saltness ought to increase in conse- 
quence, and the liquid mass would constantly diminish, if a current set- 
ting in from the Atlantic through the Straits of Gibraltar did not restore 
the equilibrium. While the less saline waters of the ocean thus pene- 
trate into the Mediterranean flowing along its surface, a submarine coun- 
ter-current, composed of heavier and Salter water, flows deep below in an 
opposite direction, and mingles with the waters of the Atlantic, which 
contain less salt. The mean saltness of the Mediterranean is nearly 38 
* See below, the chapter headed Currents, 



INEXHAUSTIBILITY OF COMMON SALT. 37 

thousandths, and even exceeds 39 thousandths on the coasts of Tripoli, 
where the parching winds of the Libyan desert blow. 

In like manner, the Caribbean Sea seems to present a somewhat high 
relative saltness because of an excess of evaporation over the contribution 
of fresh water; but the contrary happens in the Gulf of St. Lawrence, in 
the North Sea, and, above all, in the Baltic and the Euxine. The saltness 
of the North Sea is in different parts from 30 to 35 thousandths, while 
that of the Baltic, a shallow sea into which so many rivers flow, and 
where the least wind disturbs the waters,* does not quite amount to five 
thousandths ; in the port of Cronstadt it is not even two-thirds of a thou- 
sandth, which is almost fresh water. As to the Black Sea, it preserves, 
even more than the Baltic, the character of a gulf of the ocean, for the 
average saltness is about half that of the Atlantic. 

These differences of salinity between the central basin of the Atlantic 
and its tributary seas are not in themselves astonishing ; but we do not 
yet know why the South Sea and Indian Ocean contain less saline matter 
in their waters than the Atlantic, unless the enormous quantity of Antarc- 
tic ice explains this difference. While the latter has a saltness of about 
36 thousandths, the water of the Pacific has less by nearly one thou- 
sandth, and the Indian Ocean contains no more than 35 thousandths of 
chemical substances. The Atlantic, however*, receives a greater quantity 
of fresh water than the other oceans, and the evaporation is probably not 
so great, on an average, as in the Indian Ocean. But nevertheless the 
gulfs of the Indian Ocean present phenomena analogous to those of the 
inland seas of the Atlantic. Thus the Red Sea, into which no single per- 
manent stream of water flows, and where evaporation proceeds with very 
great intensity, shows the enormous degree of saltness of 43 thousandths; 
such a proportion as is only found in inland salt-water lakes.f 

Chloride of sodium or common salt contributes, as we have said, three- 
quarters of the saltness of sea-water. This is, indeed, the characteristic 
salt of the ocean which most of all gives it its peculiar flavor, and that 
odor with Avhich the sea-breezes, laden with the fine spray of the waves, 
are charged. The air which rests on the sea also contains salt to a con- 
siderable height ; at an elevation of 2000 feet above the coast on the sides 
of the mountain which towers above the Peruvian town of Iquique, Mr. 
BoUaert asserts that any materials washed in distilled water are covered 
in a few days by a slight incrustation of salt. J 

The thickness which a layer of chloride of sodium in the open sea would 
form, if crystallized, would be, on an average, nearly two inches to every 
fathom of water ; so that if one could imagine the entire evaporation of 
the waters of the ocean, estimating them to be, on the average, above 
three miles deep, there would remain at the bottom of its bed a layer of 
salt of about 230 feet in mean thickness, which would represent for the 
whole extent of the seas more than a t^usand millions of cubic miles. 

* Von Sass, Zeitschrift fur die Erdkunde. 

t Forchhammer, Philosophical Transactions, part i., 1865. f Antiquities, p. 258. 



38 



THE OCEAN. 



We can understand how, with such* vast quantities of chloride of sodium 
in solution, the sea has been sufficient to form those enormous beds of 
rock-^alt that are found in the earth in various parts of Europe, without 
I'eckoning many other deposits which still remain to be discovered, and 
which sooner or later will be repealed to us by the labors of miners, or 
by Artesian borings. 

Then, too, we may see the ocean at work on all the low coasts, where 
it deposits saline beds, destined to become in process of time masses of 
rock-salt, after they shall have been buried beneath more modern strata. 
When, in consequence of a tempest or of a high tide, the waters of the 
ocean are spread in a thin sheet over a flat shore, or in some deeper de- 
pression, this slight bed of salt water, spread over a vast surface, evapo- 
rates rapidly under the rays of the sun, and leaves in its place a slight 
white crust of saline crystals. Other sheets of water, urged by the bil- 
lows or the tide into the same basin of evaporation, disappear likewise, 
forming new layers of crystals ; it is thus that real banks of a considera- 
ble thickness are gradually formed on the borders of the sea, as well as 
on the shores of inland seas and salt lakes.* 




Pig. 10. — Salt Marshes of Bessarabia. 

Even the Black Sea, where the proportion of salt is relatively very in- 
considerable, is, on the greater part of its shores, bordered with these 
natural salt marshes. In Bessarabia, to the south of Odessa, three Umans 
of a total area of many square miles, cease in summer to receive their 

* See the section entitled Lakes. 



ELEMENTS CONTAINED IN SEA- WATER. 39 

* 

affluents of fresh water, and all the water which has been brought there 
in winter evaporates, leaving an incrustation of salt ; toward tlie centre 
of the basins of crystallization the solid mass attains nearly an inch in 
thickness.. In 1826, these natural deposits, worked by the natives, pro- 
duced about 120,000 tons .of pure salt.* In most of the populous coun- 
tries of Western Europe, man has converted these casual swamps into 
salt marshes with regular outlines. The unequal depressions, where the 
water of the sea evaporated accidentally, are transformed into reservoirs, 
where the water is conducted from compartment to compartment, to sat- 
urate itself gradually and deposit the pure salt in equal layers. But 
these are only economical works ; man is confined to regulating the oper- 
ations of the sea itself.f 

Besides common salt, many substances which are exceptionally found 
in inland Avaters and hot springs form a part of the normal composition 
of sea-water. The various simple substances which science has been able 
to discover therein (either directly by the analysis of the liquid, or in- 
directly by the.study of the plants which draw all their nourishment from 
the ocean) are twenty-eight in number; but doubtless numerous other 
simple substances are likewise contained in sea-water, many of which will 
not long escape the piercing researches of chemists. 

After oxygen and hydrogen, which constitute the liquid mass itself, the 
principal elements contained in sea- water are : chlorine, nitrogen, carbon, 
bromine, iodine, fluorine, sulphur, phosphorus, silicon, sodium, potassium, 
boron (?), aluminium, magnesium, calcium, strontium, barium. The com- 
mon fucus and other sea-weeds contain the greater part of these sub- 
stances, as well as several metals. They have discovered copper, lead, 
and zinc in the ashes of Fucus vesiculosus ; cobalt, nickel, and manganese 
in those of the Zostera marina. Iron may be obtained directly by an 
analysis of sea-water, and finally silver is found in a zoophyte, the Po- 
cillopora. Forchharamer has obtained from a branch of this coral about 
a three-millionth of silver, mixed with six times the same quantity of cop- 
per, and eight times of lead. A slight proportion of silver is precipitated 
on the bottoms of ships, in consequence of the magnetic current estab- 
lished between the copper sheathing and the «water of the surrounding 
sea. J And, lastly, arsenic has been found in the boilers of steamers which 
have been supplied with sea-water.§ It is true that these various sub- 
stances only exist in infinitesimal proportions in the water, and it is by 
indirect means alone that chemistry succeeds in revealing them ; but the 
total mass of silver contained in the ocean is estimated at two millions of 
tons. 

The seas having most probably received from the terrestrial strata, 
which have been unceasingly worn away by the currents of water, all 

* Bischof, Lehrbuch der chemischen und physikalischen Geologic. 

t See below, the section entitled The Works of Man. 

X Philosophical Transactions, part i., 1865. 

§ Bischof, Lehrbuch der chemischen und physikalischen Geologie. 



40 THE OCEAN. 

the substances which they contain in solution, we may conclude that the 
proportions of these substances have continually varied during the geo- 
logical eras. The saltness would be modified from age to age, according 
to the various quantities of soluble substances which the rivers brought 
down to the ocean, and which it returned again to the land, either direct- 
ly, by depositing them on the shore, or indirectly, by fixing them in the 
tissues of its plants, corals, and other organisms which people its expanses. 
By ingenious comparisons between the conditions of the present day and 
those which seem to have existed in former times in the sedimentary beds, 
several geologists have attempted to determine if the substances in solu- 
tion in sea-water have augmented or diminished. But the conclusions at 
which they have arrived rest, at present, on data too hypothetical for us 
to regard them as a new conquest of science. It is only certain that in 
our day the proportions of the substances dissolved have not ceased to 
vary in every sea. We can judge of this by the enormous difi"erence that 
there is between the saltness of the waters of the Caspian and those of 
the Black Sea — two separate basins which formed a part of the same 
ocean at a geological epoch still comparatively recent. 

Sea-water contains also a great quantity of the atmospheric gases, the 
proportions of Avhich constantly change with heat, light, the motion of 
the waves, and barometric pressure. Salt water retains dissolved air bet- 
ter than fresh water, and the bulk which it absorbs is generally greater 
by a third than that found in rivers. It varies from a fifth to a thirtieth, 
and gradually increases from the surface to a depth of about 325 to 380 
fathoms.* Carbonic acid gas is also contained in a relatively very con- 
siderable proportion iu sea-water, as might have been expected from the 
swarming myriads of marine animals. Under the influence of light, 
plants decompose this gas, which diminishes during the day, and is in- 
creased again during the night. As to the quantity of dissolved oxygen, 
it varies inversely ; during the day it increases by degrees, to be again 
reduced in the hours of darkness. As by a sort of respiration, the great 
sea — that immensity alive with organisms — absorbs and disengages alter- 
nately the gases necessary to the maintenance of life, and measures each 
breath by the daily course of the sun. 

* Bischof, Lehrbuch der chemischen und physikalischen Geologie. 



ITS VARIETY OF COLOR. ' 41 



CHAPTER IV. 

VARIOUS COLORS OF SEA- WATER. — REFLECTIONS, TRANSPARENCY, AND PROP- 
ER COLOR. TEMPERATURE OF THE DEPTHS OP THE SEA. 

Owing to the double property which water possesses of reflecting 
liglit and allowing its rays to penetrate to a great depth, it presents suc- 
cessively the most varied colors, the most delicate tints?, with alternations 
the most fugitive and changeable that are to be found in nature. The 
sea produces, and at the same time modifies, the varied face of the heav- 
ens with all the play and gradation of light and shade. At dawn, the 
surface of the water is gently brightened by the glimmering of the at- 
mosphere, as yet pale and faint ; then the sparkling of the waves becomes 
more brilliant, and the full light of day pours a flood of fire upon the bil- 
lows. The least movement in the air is betrayed by a change in the as- 
pect of the water, every cloud in passing mirrors itself with the forms 
and shades of its vapors, every breath of wind that just curls the waves 
renews the harmony of the changeable coloring on the face of the ocean. 
And when evening comes, the sea reflects back to the sky all its splendor 
of purple and flame. It is then that we see on the horizon "two suns 
appear, one in front of the other." 

But the water does not owe its beauty to the splendor of the sky 
alone, it is beautiful also from its transparency; while the substances 
suspended in the liquid mass, which are visible to a considerable depth, 
modify by their own color the general tint of the sea. The animals, fish 
or cetaceans, which come to the surface or glide swiftly through the 
waves, cause them suddenly to glitter with changing reflections of gray, 
rose, green, and silver. The fuci, too, growing beneath the water, vary 
the aspect of the liquid strata which cover them ; and where these beds 
of plants alternate with ridges of bare rock, or tracts of sand, the sea pre- 
sents a wonderful mixtui-e of diflerent shades with blended and tremu- 
lous outlines. In those latitudes where the water is very transparent, 
the color of the ground may be thus distinctly seen at 10, 20, or even 25 
fathoms below the surface, which navigators have confirmed by scien- 
tific observations made with the greatest care.* But this transparency 
does not seem to depend upon the intensity of light received, for in the 
^Vrctic Seas floating objects can be perceived at as great depths as in 
the Caribbean Sea ; and it is indeed in polar latitudes that the eye of 
man has been able to penetrate to the greatest depth below the surface. 
According to Scoresby, that conscientious explorer of the polar seas, the 
sea-bed of the pure waters in these regions is sometimes visible at a 
* Ciakli, Sid Moto Ondoso del Mare, p. 284. 



42 THE OCEAN. 

depth of 70 fathoms.* It is true that, in consequence of climatic differ- 
ences and the organic life which depends on them, the bottom of the sea 
is much more curious to contemplate in the tropical zone than in the 
neighborhood of the poles. There is nothing more delightful than to sail 
over one of those seas where, without fear of hidden rocks, one can watch 
the bed of the sea reveal itself far below the prow of the vessel. Numer- 
ous algge, green or rose colored, wave gracefully below the surface like 
the grasses of a brook; the mollusks crawl along the bottom; crustace- 
ans, fish, star-fishes of brilliant colors, and many other animals of strange 
form, glide slowly or dai-t like arrows thi'ough the blue water, glistening 
in a thousand changing hues; while the IsTemertida and other living 
ribbons softly unroll their transparent rings. One might fancy one's 
self suspended above another earth, and floating in an aerial ship. The 
white foam on the waves raised by the keel of the ship, and the irides- 
cent colors which sparkle in the spray, add fresh charms to this wonder- 
ful picture. 

Even when the bed of the sea is not distinctly visible, it does not fail 
to reveal itself by the peculiar tint it imparts to the water. In general 
the color of the sea is lighter near the coasts, and even at a depth of 
above 100 to 150 fathoms, a paler shade of the water at times makes 
known to the practiced eye of the mariner the relative proximity of the 
bottom. Not far from the coasts of Peru, De Tessan perceived that the 
sea had suddenly assumed a tint of dark olive-green, and when he caused 
a sounding to be taken, it was found that the mud at the bottom was 
precisely of this color. Numerous navigators have affirmed that in one 
part of the Lagullas bank, where the mass of water is above 100 fathoms 
deep, the water passes suddenly from blue to a greenish color.f Lastly, 
off Loango, the water is always brown, similar to that of the bottom, 
which Tuckey has found to be of an intense red. Is, then, this coloring 
owing to the sun's light, which descends through the liquid depths to 
the bed of the sea, and is reflected again to the surface ; or does it result, 
as Cialdi thinks, from particles of mud that are floating in the water ?J 

Another question, difficult to solve, is that of knowing what is the nat- 
ural color of the sea- water. Not to mention local coloring, resulting, like 
phosphorescence, from numberless minute living organisms,§ the various 
parts of the ocean almost always present, whatever may be the state of 
the atmosphere, a normal tint easy to be distinguished from accidental 
shades. Thus, to cite one of the most striking contrasts, the water of the 
Gulf of Gascony is of a sombre green, while in the Gulf of Lyons the 
water of the Meditei-ranean is of a magnificent azure, deeper than that 
of the sky. The wonderful blue color which rises from the depths of 
the water in the grotto of Capri, so frequently visited by travelei-s, is a 
well-known example of the degree of intensity to which the blue peculiar 

* Arctic Regions. See also the notice of Arago, (Euvres coinpletes, t. ix. 

t Arago, ibid. % -SmZ Moto Ondoso del Mare, p. 287. 

§ See below, the section entitled The Earth and its Fauna. 



TEMPERATURE OF THE SEA. 43 

to the waters of the Mediterranean can»attain. In the tropical latitudes 
of the Atlantic and the South Sea, the azure of the ocean is no less beau- 
tiful than that of the Tyrrhenian Sea; Avhile in the direction of the poles 
the water gradually assumes a greenish tint. Naturalists have con- 
cluded from this fact that the refraction of the rays of light, which are 
much more vivid under tropical latitudes, play a principal part in the 
blue coloring of the sea. Maury thinks that the saltness is also one of 
the causes which contributes the most to give its azure tint to the wa- 
ter ; and x)bserves that the Gulf Stream of the American coasts, superior 
in salinity and in temperature to the water around it, is also of a much 
deeper blue. In the same way the shallow water let into the salt marshes 
of coasts gains in intensity of color in proportion as the salt is concen- 
trated there. Still, it is very possible that th^ coloring of the sea is due 
in great part, like the marvelous tints of the Swiss lakes,* to innumerable 
corpuscules held in suspension, upon which the light strikes. 

The law of the distribution of temperature, in the depth of the ocean, 
is not as yet more determined than that of the coloring of the water. 
At the surface of the sea it is as easy to make observations as in the air, 
and it has been determined, without difficulty, that this superficial sheet 
of water presents, on an average, in all climates, the same degree of heat 
as the superincumbent atmosphere. Thus, from the polar regions to the 
equatorial zone, the water becomes warmer with an almost regular grada- 
tion, and, from the freezing-point under the Arctic circle, the temperature 
rises to 68 and 77 degrees Fahr. under the tropics, and to 86 and even 
above 90 degrees Fahr. in the Pacific, the Red Sea, and the Indian Ocean. f 
With regard to the increase or decrease of heat in a vertical direction, we 
had till recently only the vaguest notions, in consequence of the want 
of exact soundings. It is, in fact, very difficult to lower to a depth of 
several hundred, and even several thousand fathoms, thermometrical ap- 
paratus strong enough to resist the enormous pressure of one atmos- 
phere for every 33 feet. 

Sir James Ross was one of the first who attempted to apply the re- 
sources of modern science to a systematic exploration of the temperature 
in the depths of the sea; but he seems to have committed the error of 
generalizmg too hastily from the incomplete results which he had obtahi- 
ed ; and, in his eagerness, he believed he had discovered a law which the 
subsequent researches of navigators have not confirmed. He thought 
that he could establish the fact that under the equator the temperature 
of the water diminishes gradually to 1200 fathoms, where it is only 39'2 
degrees Fahr. On each side of the equator the upper waters gi-adually 
cool, and the limit of four degrees is progressively raised toward the sur- 
face ; it is at the fiftieth degree of latitude, in the southern hemisi^here, 
that it finally reaches the level of the sea. Farther in the direction of 
the pole the superficial water continues to grow colder, while the line of 
four degrees sinks gradually to the depth of 765 fathoms. Thus, as the 
* See the section entitled Lakes. t Fitzroj, Weather-Bool-, p. 84. 



44 



THE OCEAN. 




::i^^iM&m. 



Fig. 11. — Sheet f)f Water presumed to be at a teropcrature of .09-2 degrees Fahr. 



accompanying figure shows, the line of uniform temperature to the south 
of the equator describes a long curve, touching the surface of the water 
at one point only. Admitting, with the naturalists of his time, that the 
sea-water has its greatest density, and in consequence its greatest rela- 
tive weight, at seven degrees above freezing-point. Sir James Ross con- 
cluded from this that all the deep waters below this line of 39"2 degrees 
have the same temperature, and are collected by reason of their conden- 
sation at the bottom of the oceanic basins, 

Nevertheless it has since been proved, by the obsei'vations of Neu- 
mann* and other scientific men, that if the greatest density of fresh water 
corresponds in reality to 39'2 degrees Fahr., the water of the sea only at- 
tains this maximum at nearly four degrees below freezing-point (28'4 de- 
grees Fahi'.), or even at still lower temperatures, and, in consequence, the 
conclusions at which Sir James Ross arrived are negatived. Experiments 
made in chemical laboratories, however,' where substances are treated in 
small quantities, can not give a perfectly exact notion of the phenomena 
which have nature itself for their theatre, and which take place either in 
the aerial spaces or in the vast oceanic basins. Thus, as the celebrated 
meteorologist Mtihry says, the immense sea, and a bucketful of salt water, 
do not obey absolutely the same laws of temperature and density. But 
before the difference is established, nothing can authorize us in maintain- 
ing a superannuated theory against all the experiments of chemists, ac- 
cording to which the volume of salt water in the sea in cooling presents 
phenomena identical with those of fresh-water lakes. Moreover, during 
the past years, numerous observers of polar seas have found at great 
depths beds of water at a temperature lower than 39'5 degrees Fahr.f 

That which remains of the researches of the eminent navigator. Sir 
James Ross, is that in the tropical and temperate seas the heat diminishes 
graduallj'- and constantly to a considerable depth. This is what has been 
put beyond all question, by soundings taken by Fitzroy and other marine 
explorers. To the south of the island of Madagascar, the surface of the 
water having then a tempei-ature of 1b'2 degrees Fahr., Fitzroy ascer- 
tained that the thermometer fell in the most regular manner, till at the 
* Ueher die Dichtigkeit heim Meerwasser. t Fitzroy, Weather-Book, p. 81. 



TEMPERATURE OF THE SEA. 45 

depth of 420 fathoms, where they ceased sounding, the temperature indi- 
cated hardly cxc(.'eded 5r8 degrees Fahr.* 

In tlie inclosed basins of inland seas thermoraetrical observations arc 
much more easily made than in the middle of the great ocean, because 
the waters there are generally less deep, and the natural gradations of 
temperature are less disturbed by currents. Thus the water is not very 
cold in the depths of the Mediterranean, and presents only slight varia- 
tions of temperature. At about 100 to 275 fathoms below the surface, 
the fluid .mass has already attained permanently the mean temperature, 
which it preserves during all the year, and which seems to correspond to 
the meam annual temperature of the neighboring lands, which are subject 
to all the abrupt changes of heat and cold.f While in summer the super- 
ficial sheet of water has about 73 "4 degrees Fahr., the water comprised 
between 273 fathoms depth and the very bottom of the Mediterranean is 
found at 59 degrees Fahr., which is pretty nearly the mean annual warmth 
of the bordering countries. In the Greek Archipelago, the deep waters 
of which are probably colder in consequence of the current flowing from 
the Black Sea, the waters of the surface have in summer from 77 to 78 '8 
degrees Fahr., and at hardly 98 fathoms' depth the thermometer reveals 
a constant temperature of from 53*6 to 55*4 degrees Fahr. The Mediter- 
ranean is divided into distinct basins, separated from one another by in- 
termediate ridges, which are situated from 98 to 273 fathoms below the 
surface, the result being that the variations of temperature produced by 
the movements of currents and counter-currents arc arrested on the tops 
of the ridges. The water of each basin, being relatively tranquil, thus 
maintains almost constantly the same thermometrical degree.]; 

* Adventure and Beagle, vol. ii., Appendix, p. 303. 
t See below, the section entitled Climates. 
X Spratt, Nautical Magazine, January, 1860. 



46 , THE OCEAN. 



\ CHAPTER V. 

FORMATION" OP ICE, — ICE-FLOES, FIELDS OF ICE, AND ICEBEEGS. — ICE IN 
THE BALTIC AND THE BLACK SEA. 

In the Polar seas the low temperature results in the formation of ice. 
During the long winters of these cold regions, the tranquil water of the 
bays and gulfs freezes round the edge of the coasts, and the crystallized 
mass gaining incessantly on the sea finally extends to a considei'able dis- 
tance. This is " ground-ice." The surface of the sea disappears, like that 
of the lakes, under a solid layer; but the manner of forming the icy crust 
differs, for in the rivers and basins of fresh water crystals of ice at first 
appear over almost the entire surface, but in the seas which have no great 
depth it is generally from the bed itself that the liquid mass congeals. 

In fact, salt water has not, like fresh water, its greatest density at the 
temperature of 39*2 degrees Fahr., but it becomes heavier and heavier in 
proportion as it freezes. The coldest strata of water, being also the 
heaviest, descend vertically toward the bottom of the sea, and displace 
the lower strata, which are lighter and of a higher temperature. While 
the water which descends to the bottom in rivers has a normal heat of 
seven degrees above freezing-point, the sea-water which falls deeper may 
have been chilled to 32° Fahr., or even many degrees below it. When 
the mass is not agitated, it remains liquid, but, on the slightest disturb- 
ance, it suddenly turns to ice. Sometimes, at the commencement of win- 
ter, the mariners and fishermen of the Baltic and western coasts of I^or- 
way find themselves suddenly surrounded by floes of ice, which rise from 
the bed of the sea and which still contain fragments of fucus. It ap- 
pears so rapidly that the boats often run great risk of being crushed be- 
tween the solid masses which are piled around them, and the crews are 
in imminent danger. Around the rocky coasts of Greenland, Labrador, 
and Spitzbergen, these* ice-floes often raise huge stones which they have 
torn from the bed of the sea.* 

In the open sea ice is also formed. In winter, when the air is calm, 
the snow falls in large flakes on the tranquil waves, the sea is soon cov- 
ered with a kind of scum,*which gradually changes into a thin coating 
of ice. The wind may break this layer when barely formed, and the 
tiny scattered fragments may be surrounded with water from the melted 
snow, which does not mix with the salt-water of the sea, and glitters 
feebly with iridescent hues beneath the rays of an oblique sun; but this 
does not last long, and the cold soon reforms the layer of ice.f Even in 

* Edlund, Poggendorf' s Annalen, cxxi. 

t Gustave Lambert, Expedition au Pole Nord. Bulletin de la Societe de Geographic, 
December, 1867. 



FIELDS OF ICE. 4-7 

despite of wind and wave, innumerable needles of ice, which give to the 
surface of the water a pasty appearance, spread their net-work over the 
sea, and soon consolidate into a thick layer, which constantly increases 
as the cold of winter becomes more and more rigorous. By the natural 
chemistry of the sea, which is an immense laboratory, the mass of ice is 
in a great measure freed from the salt which is found in sea-water; for, 
according to the observations of Mr. Walker, it contains hardly more 
than five thousandths; that is to say, about a fifth of its normal quantity. 
The water nearest to the new ice mixes with the expelled salt, becomes 
heavier, and as the freezing-point is at the same time lowered it descends 
deeper in the water without becoming solid. This is the reason why in 
the open sea the water is rarely frozen for any considerable depth, below 
the surface, as one might expect.* 

In consequence of the frequent collision of these fragments of ice toss- 
ed by the waves, they generally assume the same circular form as the 
flakes of ice on rivers. They are roundlets of a very inconsiderable di- 
ameter, slightly raised at the edges ; the English sailors term them " ice- 
cakes." But the cold becoming more intense, these disks finally adhere 
to one another, and before long millions of them, united in vast fields, 
form islands which stretch to the farthest horizon. Sometimes these 
" ice-fields " have a superficial extent of hundreds of thousands of square 
miles, and even constitute, by their dimensions, real continents. Those 
which border upon the eastern coast of Greenland have not been melted 
for four centuries, and efiectually prevent the approach of navigators to 
the land ; those connected with the Siberian coasts are still more con- 
siderable, because of the long extent of shore which serves as their base. 
In the Polar archipelago of America, ice bars the entrances of the chan- 
nels almost every year, and raises before the navigator an impassable 
wall. How many times have the explorers of Arctic seas tried in vain 
to find a passage through these barriers, and have remained imprisoned 
in the solid mass, after having ventured into some deceitful opening of 
the ice-field ! 

These interminable white surfaces are almost always bordered on the 
seaward side by blocks and disks rocking or whirling on the billows; 
these are the scattered islands which announce the neighborhood of con- 
tinents of ice. Those which are elevated on an average from three to six 
feet above the water, and the bases of which descend from twenty to 
twenty-five feet below the surface, have sometimes a tolerable uniformity 
of aspect, and when at times the snow covers all inequalities, the ice-field 
seems to be transformed into an even plain like the Russian Steppes. 
But the ice is much more often rugged ; fantastic hillocks, formed of all 
the wreck-fragments which the floes of ice have thrown up in dashing 
against each other, appear here and there several yards high. There are 
some which one might even confound with the enormous blocks that 
have fallen from the glaciers of Greenland or of Spitzbergen, and which 
* Neumann, Ueber die Dichtigkeit heim Meerwasser. 



48 THE OCEAN. 

really can not be distinguished from them but by the slightly saline 
taste of the ice. These projecting masses are seen from afar above the 
sea, and remain erect long after the ice-field has melted. In the Siberian 
seas, where they give them the name of toroses, most of these hillocks, 
composed of the ice of the preceding winter, are easily melted by the 
•first warmth of summer ; but there are some which are preserved from 
year to year, and which remain indestructible during centuries, even un- 
der the rays of the sun. The Ostiac hunters, who frequently see these 
toroses run aground on the Siberian coast, designate them "Adam's ice," 
and, imagining that they are contemporaneous with the origin of the world, 
assert that even fire itself is powerless against their crystalline masses.* 

In spring-time and in summer, when the great heat commences in the 
polar zone, the force of the currents, whose action constantly makes itself 
felt beneath the ice plains, detaches from the remainder of the mass 
enormous fields of ice several hundred square miles in extent, and carries 
them far toward the open sea. The vessels of the explorers or whalers, 
which have been set fast in the bed of ice, are then carried out of their 
course with the broken field. Coui\ageous sailors who have penetrated 
beyond Bafiuln's Bay have often thus been brought back by the current 
for hundreds and thousands of miles, and have only been able to regain 
the way they have lost at the price of most painful efforts, or have 
even been obliged to abandon their enterprise completely. Such was 
the case in the sea around Spitzbergen in 1777 ; ten Dutch vessels were 
driven with the ice more than 1500 miles toward the south-west, and 
shattered on the way. It was a phenomenon of the same nature which 
prevented CajDtain Parry from reaching the North Pole. He had al- 
ready approached nearer to this point than all preceding navigators, and 
had taken a sledge to cross the ice-field ; but each day, notwithstanding 
the great distance apparently traversed in the direction of the pole, he 
found himself farther than the day before from the goal toward which he 
marched — the reason being that the continent of ice which bore him was 
being itself carried rapidly toward the south. White bears are thus 
sometimes carried by ice-floes, and landed on the coasts of Lapland.f 

When once broken, the ice-field soon disappears ; large fragments, driv- 
en by the currents and the waves, are dashed against each other with 
the enormous force which a weight of hundreds of thousands or millions 
of tons gives. Shattered by the terrible shock, these masses are divided 
into pieces of smaller dimensions ; the cementing ice being destroyed by 
the fragments of the more anciently-formed ice-field, the turrets and pin- 
nacles which stand here and there begin to melt and fall, and a few days 
after the thaw has commenced nothing remains but a few ice-floes and 
uneven blocks gently rocking with the waves. To account for this rapid 
disappearance of the ice-fields (in which the infinite tiny organismsj of 

* r. de Wrangel, Voyage, Appendice, p. 314. 

+ Barto von Lowenigh, Mittheilungen von Petermann, Erganznngsheft xvi. 

X See below, the section entitled Earth and its Flora. 



FORMATION OP ICEBERGS. 



49 



tlie sea also aid) the inhabitants of Greenland imagine that the entire 
mass is ingulfed iu the depths of the ocean. Even in the Baltic, where 
this phenomenon is comparatively much less remarkable, the Danish 
sailors, almost without exception, assert that in spring-time the ice-floes 
are swallowed* up by the sea, although not one of them has witnessed 
the immersion.* But what is more easily corroborated is the strange 
noise that always accompanies the breaking up of the ice. With the 
crash of the meeting ice, more deafening, more terrible than that of can- 
non answering to each other, with the roar of the waves, and the groan- 
ing sound from the breaking disks and the air which escapes from them, 
is-joined a kind of crackling, similar to drops of rain falling on plates of 
metal. This noise, which is heard also on mountain glaciers, results, as 
Tyndall has shown, from the incessant breaking up of the crystals which 
compose the mass.f • 




Pig. 12.— Glacier of La Madeleine, ou the Coast of Spitzbergen. 

Whatever picturesque beauty thei-e may be in the ice of marine forma- 
tion constituting this field, it is far inferior to that of the masses which 
are detached from the glaciers of Greenland, Spitzbergen, and other coun- 
tries of th^ North Pole, Enormous fragments may be separated from 
the end of the glacier in two different ways, according to the tempera- 

* Forchhammer, Philosophical Transactions, part i., p, 233, 1865. 
t See the chapter entitled Snows and Glaciers. 
4 



50 THE OCEAN AND THE ATMOSPHERE. 

ture of tlae sea into which they protrude. In Spitzbergen and on the 
coasts of Southern Greenland, the congealed mass, which often projects 
far into the sea, is gradually undermined by the comparatively warm 
waves which beat against it, and the remaining fragments overhanging 
the water are detached with a terrible noise, and plunge into the ocean. 
M. Martins and other members of the French expedition to Spitzbergen 
have observed this at the base of all the glaciers of that archipelago. But 
in very cold seas, like that of Smith's Strait, the water, being of a still 
lower temperature, can not melt the glacier, which continues its course 
into the bay, its extreme end reaching fai? into the depths of the ocean, 
like an immense plain gliding over the rocks. Though lighter than the 
water, the enormous frozen mass is kept below because of its cohesion to 
the mer-ch-glace which drives it along. But the moment comes when that 
connection breaks, and, obeying at last the force which its buoyancy im- 
parts to it, it shoots to the surface, and after repeated oscillations from the 
change in its centre of gravity it rises in huge towers or fantastic peaks.* 
We can imagine what a chaotic mass all these fragments, mixed with the 
marine ice and the remains of ice-fields, must produce in narrow bays, or 
in very contracted arms of the sea. It was across one of these prodig- 
ious " packs," in Smith's Strait, that the inti-epid Hayes, wuth almost su- 
perhuman perseverance, passed. 

These glistening icebergs are the splendor of Arctic seas. Often of 
colossal dimensions, they present at times forms of almost perfect regu- 
larity, while at others they assume the most varied and fantastic shapes. 
Lofty towers, columns in pairs, with groups of sculpture, and statues, 
like marble divinities, rise above the sea. In comparatively warm seas 
like those of Spitzbergen, which are a^cted by the Gulf Stream, the ice 
is constantly worn away ; and those parts of the floating masses which 
rise above the surface of the sea generally assume the appearance of pil- 
lars, with more or less overhanging capitals, fringed with stalactites. 
The summit is white and occasionally covered with snow, Avhile the flut- 
ing of the column where the more compact ice has been bathed by the 
waves has an emerald or sapphire hue. The foundations of the columns 
are pierced with caves, into which the water rushes with a hollow mur- 
mur ; and at times they are riddled with small holes, from which each 
wave springs in diA^erging jets. Silvery fountains burst alternately from 
either side of the column, according to the inclination given to it by the 
sea,f In very cold water, like that of the Arctic Ai'chipelago, the op- 
posite phenomena occur. Instead of being worn away and melted by 
the waves, the blocks fallen from the glaciers at first gradually increase 
in dimensions, on account of the low temperature of the water iftto which 
they are plunged, which solidifies around the foot of these enormous 
floating towers.J 

* Rink ; Hayes, The Open P.olar Sea. 

t Bavto von Lowenigh, Mittheilungen von Petermann, Erganzungsheft xvi. 

X Edlund, Poggendorfs Annalen, 6xxi. 



SIZE OF THE ICEBERGS. 51 

The larger masses detached from the glaciers are known i;nder the 
name of icebergs. Dr. Wallich was able to measure some of them on 
the coasts of Greenland, by ascertaining the depth below water of the 
bank on which several of these moving bergs had been stranded ; and he 
found that, with the regularly formed blocks, the part above the level of 
the sea is never more than the fourteenth or sixteenth part of that be- 
neath the level of the water. With respect to the masses whose exposed 
portions terminate in a cone or a pyramid, they descend to a less depth, 
in proportion as they present a more considerable bulk above water. 
But the total height of the iceberg always exceeds by seven or eight 
times the visible portion. 

By these proportions, mariners can judge of the real size of the icy 
masses which they see stranded on the coasts of Newfoundland, or melt- 
ing slowly as they float far out into the Atlantic. Enormous blocks have 
been seen from 800 to 400 feet high, so that these fragments of glaciers 
measured more than 3000 feet from summit to base — that is to say, an 
elevation equal to the highest mountains of England or Ireland. One 
of these masses which was encountered by the ship Acadia off the Banks 
of Newfoundland, amidst a labyrinth of other floatiag mountains, was 
about 480 feet high, surmounted by a kind of dome resembling St. Paul's 
Cathedral in a most singular manner. Twenty days later, when on her 
homeward voyage, the Acadia found the same iceberg 68 miles more to 
the south. A great number of these traveling masses have been seen, 
measuring several miles in length and breadth, whose bulk amounted to 
tens of thousands of cubic yards. As to fragments of ice-fields, some 
have been met with measuring not less than from 50 to 100 miles in each 
direction. 

TJie slow movement of the block observed by the Acadia^ which only 
advanced a little more than three miles per day, proves that icebergs 
offer considerable resistance to the current which carries them. The 
checks to which they are subject on the way, such as partial strandings, 
or when the surface and under-currents urge them in opposite directions, 
retard their speed considerably, and often change them into seemingly 
stationary islets. Toward the end of 1855 an unexpected circumstance, 
still moi'e remarkable than that of the berg seen by the Acadia^how^ us 
exactly what had been the progress of an iceberg during the space of 
more than a year. An American whaler sailing in Davis's Strait per- 
ceived a dark mass in the middle of a group of floating peaks ; this mass 
was the ship Resolute^ which the British Government had sent out in 
search of Franklin, and which the crew, having ventured into the ice-pack, 
had abandoned, to continue their way in sledges. When the vessel was 
found again, it had been already detained in its floating prison for six- 
teen months, and during that space of time had only been carried about 
870 miles, counting the necessary turnings through Barrow's Strait and 
Lancaster Sound. Thus the ship, abandoned in the Polar Sea, had not 
exceeded the speed of 130 yards j^er hour in its progress toward the At- 



52 THE OCEAN. 

lantic, which is a hardly perceptible advance. In the history of the 
great Arctic expeditions thi-ee other vessels are mentioned, which were 
carried in the same manner toward the ocean, but without having been 
abandoned by their crews; these were the ships of Sir John Ross, of 
Lieutenant De Haven, and of McClintock, The last-named navigator 
was a prisoner for 242 days, and advanced about 1120 miles toward the 
south, that is to say, about 346 yards per hour. 

The enormous masses of icebergs, like gigantic ships, are often stranded 
on shoals, even where the depth of the sea exceeds a hundred fathoms. 
Arrested in its southward drifting, the immense block gradually dissolves 
or divides into fragments, which in their turn are stranded on some other 
bank at a less depth. Day by day the waves melt and destroy great 
quantities of ice, which then let fall the gravel and stones with which it 
was charged, and in this manner continually raises the sea-bottom. Ev- 
ery year new beds of rock, pebbles, and earth from the mountains of 
Greenland and the archipelago of North America are thus deposited on 
the Banks of Newfoundland and in the neighboring seas, laying the 
foundations of a new continent. Doubtless the Great Bank, which ex- 
tends over a tract of above 55,000 square miles, and which has its foun-, 
dation in a sea of about four to six miles deep, is composed entirely of 
this moraine matter of glacial origin. Thus during a long series of ages 
the ice-floes have been laboring without relaxation to demolish the Arc- 
tic lands, and to construct new continents in the seas of the temperate 
zone. 

From the time of the breaking up of the northern ice — that is to say, 
from the beginning of March to the month of July and even to the 
month of August — that part of the Atlantic to the east of the Banks of 
Newfoundland assumes the appearance of the Arctic Sea. The Polar 
current, descending from Baffin's Bay parallel to the coasts of Labrador, 
brings with it in long procession the fragments of the ice-fields and gla- 
ciers of Greenland. After having rounded the Banks of Newfoundland, 
the current bends toward the south-west with its burden of ice, in conse- 
quence of the movement, which carries the earth in an easterly direction, 
and causes a deviation from its course in every thing coming from the 
north.* fCarried by this current, which drives them in the opposite di- 
rection to the Gulf Stream, continuing its course toward the south-west 
below the surface current of the latter, the icebergs, like ships cutting 
the waves with their prows, pass majestically through the water which 
dashes against them. Some fragments of mighty ice-fields, brought from 
Greenland by Polar currents and then drifted northward by the Gulf 
Stream, S.re seen here and there proceeding in an opposite direction from 
the rest. The accompanying map, borrowed from Redfield, indicates the 
position of all the icebergs and ice-fields recently observed in the western 
part of the North Atlantic Ocean. • 

It is principally in this region of the ocean that flotillas of ice are to 

* See below, p. 68. 



DANGERS FROM ICEBERGS. 



53 




Fig. 13. — Course of the Icebergs between Europe and America. 

be dreaded' by navigators. The sailors of Newfoundland hardly ever 
approach one nearer than about a mile, and then always keeping to 
windward of them, for otherwise they would be in danger of drifting 
upon the terrible mass, toward which, in addition, a somewhat strong 
current is always flowing to replace the upper ^tratum of water, rendered 
colder by contact with the floating mountain. Enveloped in fog, in con- 
sequence of the lowness of their temperature compared with that of the 
warm, humid air from the south, the gigantic hull of the glacier discovers 
itself to seamen by strange whitish reflections, and also by the intense 
cold of the surrounding atmosphere. But sometimes, when this indica- 
tion of peril has just been recognized, it is too late to avoid the shock. 
Hundreds of ships overtaken by the ice have thus disappeared, with 
their crews, in the cold waters of the ocean. At other times, even in 
clear weather, one meets with a whole archipelago of ice-floes ; and, in or- 
der to avoid them, it is necessary to steer with the greatest precaution 
for days together. It Avas thus that, in 1821, the English brig Anne, sur- 
prised by the ice before Cape Race, not being able to enter a free sea, 
was obliged to remain twenty-nine days surrounded by towers and 
threatening peaks. Happily these fragments of glaciers diminish very 
quickly in number and height as soon as they enter the zone of the 
Gulf Stream. Worn away at their base by the tepid waters of that cur- 



54 



THE OCEAN. 



rent, they capsize, break, and dissolve so completely, that toward the 
40th degree of latitude it is rarely that any fragments even remain. 
However, in June, 1842, the ship Formosa encountered, in 37° 30' of 
north latitude, a floating iceberg 30 yards high and 50 yards long mov- 
ing toward the south.* 

In the Antarctic hemisphere exactly similar phenomena occur. Thus, 
as is proved by numerous observations, more than 860 of which have 
been regularly catalogued by Fitzroy and other geographers, the ice- 
fields and fragments of glaciers of the southern continent float likewise 
in the direction of the equator. But it seems that the icebergs of the 
southern hemisphere generally present less variety of form than those 
of the opposite one. They are not peaks and domes with fantastic out- 
lines, but rather resemble walls rising like rocky precijDices to an eleva- 
tion of about 160 to 200 feet; these floating masses are probably, how- 
ever, on an average of still more considerable dimensions than the masses 
which fall from Arctic glaciers. The massive form of these floating 
mountains of the southern seas must doubtless be attributed to the 
severe cold which prevails in the south jDolar zone, which drives the 
snow and glaciers of the Antarctic lands farther into the open sea. Even 




Figs. 14 and 15.— Icebergs of the Autarctic Ocean (after Wilkes). 

at the 50th degree of south latitude, ships meet with ice-fields of a size 
equal to those which on the other side of the earth are only found with- 
in the polar circle. In the northern hemisphere the ice-rivers of Green- 
land and Spitzbergen are not fed by a sufiicient quantity of snow to car- 
* Eedfield, Memoir on the Dangers of Ice in the North Atlantic Ocean. 



The Ort-au.&f. 



A N T A R 



j3o Eas 



A C 



I I I 






Engraved ly E rliar d . 



HARPER. &. B] 



I C LAND 




B a ^ s^ _. ^ Ur a i t s 



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Diawn by A. VuiUemin ."_ ajLcr Ch .Wilkes 



THE ANTAECTIC ICE- FIELDS. 



55 



ly tlieni completely out of the bays into which they flow, and into the 
open sea. Retained in their course by steep lateral cliffs, promontories, 
and rocky islets, they assume, in consequence of all these obstacles, a 
much more irregular form than they would have if they penetrated into 
the free ocean, like the glaciers of the South Pole. The latter are drift- 
ed for out of the gulfs, beyond the capes even, and they are only oc- 
casionally attached to the submarine base of the continent. In front of 
this ice-sheet float innumerable islands, through which ships can with 
difliculty find their way. Thus during the exploring voyage of Wilkes, 
the Peacock had to steer for a long time in a labyrinth of blocks which 
threatened to crush her. 




16.— Route of the Peacock, Commander Wilkes, U. S. Navy, in the Antarctic Ice-paclc. 



The breaking up of the Antarctic ice occurs in spring and summer, 
like that of the North Pole, but six months later, in consequence of the 
opposition of seasons in the two hemispheres, caused by the obliquity 
of the earth's axis. The scattered pieces of ice met with during winter 
are only fragments detached from the ice-fields. Vessels traversing the 
Antarctic Ocean meet with thirty or forty times more ice in December, 
the height of summer, than in July, which is the coldest time. The niul- 



56 



THE OCEAN. 



titude of floating masses varies much in these seas. To the south of 
Australia and New Zealand icebergs and ice-fields are comparatively 
rare. To the south of Cape Horn they are met with more frequently, 
but are never seen between this southernmost point of America and the 
Falkland Islands ; for, owing to the great Polar current, they all drift 
toward the north-east. It is to the south of the African continent that 
the ice is carried in the greatest quantity, and approaches most nearlj^ to 
the equator. Some has even been perceived from Cape Town in 34 de- 
grees of south latitude. Thus the Antarctic icebergs are carried about 
250 miles nearer the torrid zone than are the Arctic masses. 





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Fig. 17. — Course of Icebergs in tlie Southern Hemisphere. 

In the inland seas exposed to severe cold, the congelation of the water 
is produced in the same way as in the ocean ; the phenomena onlj^ differ 
^in proportion. Thus the ice of the Baltic is far from presenting such a 
grand spectacle as the ice-fields of the Polar seas, but its mode of forma- 
tion is known in a much more complete manner; for dujing a long se- 
ries of years, conscientious observers have studied its various changes, 
from the formation of the first ice to the general breaking up. These 
researches have proved that, after having been formed, the icy bed of the 
Baltic is subject to the same phenomena as that of lakes, not only in the 
northern parts of the sea, where the water is almost fresh, but near the 
entrance also, where the mass of fluid is still strongly saline. The cre- 
vasses in the ice do not differ essentially in their foi'mation from those of 
Lake Baikal* or the Lake of Constance. They also open with a thunder- 
ing noise, letting a great quantity of water escape, which freezes in its ' 
turn, and thus increases the thickness of the solid bed. Around the isl- 
and of Oesel the fissures vary from six inches to more than six feet, and 
are continued for a distance of several miles. But the surf produced by 

* * See the section entitled Lakes. 



THE ICE OF THE BALTIC. 57 

the cuiTents and the dashuig of the waves, where the sea is not frozen, 
o-ives the most varied directions to the crevasses ; in some places they 
are parallel, while in others they intersect one another irregularly, or ra- 
diate toward all points of the horizon. 

Ice very rarely covers the surface of the sea while the water is much 
ao-itated. Tempests or rapid currents retard, or even completely pre- 
vent, the formation of the ice-sheet. Thus, while on the east, where the 
sea is calm, the island of Oesel is, on an average, united to the main-land 
durino- 130 days of the year by a layer of ice sometimes attaining a 
thickness of more than three feet, and serving as a high-road for sledges, 
the w^estern cliiTs, against which the surges strike, are, on the contrary, 
only bordered by a narrow fringe of ice. On the promontory of Muhha 
'Ninna the waves always break with fury, and this extreme agitation of 
the water lasts during the whole winter, preventing the appearance of 
the least particle of ice ; indeed the peasants of the island say that they 
have never seen any near this point.* 

Every year a considerable part of the Baltic is covered with ice. Al- 
most all the Gulf of Bothnia and the entire coast-line of the Gulf of Fin- 
land is changed into a white and immovable surface, the island^ and 
islets are encircled by a zone of ice-floes, more or less wide, while the 
straits of a slight depth are similarly obstructed. Every winter Finland 
is reunited to Sweden by a bridge of ice, pierced here and there by the 
innumerable rocks of the Oeland Archipelago. This solid crust then be- 
comes for many months the highway between Sweden and Russia. The 
Baltic, like the Polar ice-fields, has its piled-up masses of ice, resembling 
turrets, pyramids, and obelisks built upon the sea ; from these fields, also, 
broad masses are detached from their edges to float toward the south 
with the current, then, breaking with a loud crash, are similarly reduced 
into scattered pieces; and in a few days after the commencement of the 
thaw only thin fragments remain, tossed here and there by the waves. 

During the last few centuries the Baltic Sea has never been entirely 
covered with a field of ice. But the chronicles inform us that in 1323 
the southern part of the basin was completely frozen over, and during six 
Aveeks travelers from Copenhagen repaired on horseback to Ltlbeck and 
Dantzic ; and temporary hamlets were even erected on the ice at the in- 
tersection of the roads. During the winters of 1333, 1349, 1399, and 
1402, the same phenomena of general congelation occurred in the south- 
ern Baltic, and the icy bed served as a road for commerce between Pom- 
erania, Mecklenburg, Denmark, and the islands. In 1408 the ice-field 
completely closed the entrance of the Baltic between Norway and Jut- 
land, and extended through the Categat, the ^traits of the Sea of Scania, 
into the Baltic, as far as the large island of Gothland. It is said even 
that the wolves of Norway, driven from their native forests by hunger, 
crossed the Skagerrack to invade the villages of Jutland. Since this 
epoch, several parts of the Southern Baltic have been frozen over again; 

* Von Sass, Bulletin de F Academic de Saint Petersbourg, t. ix., p. 166, etc. 



58 THE OCEAN. 

but the solid surface has never presented the same extent, nor the same 
consistency. This fact would seem to prove that the mean temperature 
has become milder in Northern Europe since the 14th century, while, ac- 
cording to Adhemar's hypothesis, exactly the contrary is the case.* 

It is a remarkable fact, that save in a few exceptional years the Black 
Sea, which is exposed to all the piercing winds which descend from the 
Polar regions, has never been invaded by ice like the Baltic, During 
the earlier historic ages the Sea of Marmora and the surface of the Eux- 
ine have been frequently covered with ice ; which proves that, at least 
during this period of frost, the temperature of Constantinople was no 
higher than that of Coj^enhagen. In the year 401 of the present era the 
Black Sea was almost entirely frozen over, and when the ice broke up, 
enormous icebergs were seen floating in the Sea of Marmora for thirty 
days. In 762 the solid layer which covered the Euxine extended from 
one bank to the other, from the terminal cliifs of the Caucasus to the 
mouths of the Dniester, Dnieper, and the Danube. Moreover, contempo- 
rary writei's assert that the j:][uantity of snow which fell on the ice rose 
to the height of twenty cubits (from 30 to 40 feet?), and completely hid 
the contour of the shores, so that one kncAV not where the land began or 
the sea ended. In the month of February, the broken masses of the ice, 
carried by the current to the entrance of the ^gean Sea, reunited in one 
immense sheet, between Sestos and Abydos, across the Hellespont. f 

* See the chapter entitled Harmonies and Contrasts. 
t P. de Tchihatcheff, Le Bospore et Constantinople. 



BE&ULAR AND IRREGULAR UNDULATIONS. 59 



CHAPTER VI. 

M'AVES OF THfe SEA. REGULAR AND IRREGULAR UNDULATIONS. HEIGHT OF 

THE WAVES. — THEIR SIZE AND SPEED. — GROUND-SWELL. COAST-WAVES. 

The sea rarely presents a glassy surface. When the atmosphere is 
calm, Avhich however is commonly the case before a tempest, the water 
is sometimes so very smooth that every object is reflected by it with a 
perfectly sharp outline ; the only changes which seem to affect the vast 
motionless sheet of water are those produced by the mirage, which 
makes the distant horizon glitter like a long band of sUver or steel ; the 
fishermen then say that " the sea is reflecting itself." But this tranquilli- 
ty of the water is a very imcommon phenomenon, except in the Mediter- 
ranean and other seas, where there is only a slight tide. Usually the 
wind, either in breezes or tempests, now aiding and now retarding the 
ebb and flow, raises the sea into waves, more or less high, which some- 
times roll onward regularly, or are dashed against and cross one another. 
Even during calms, the waves, still obeying the impulse of recent winds, 
continue to roll across the ocean in long undulations. One of the grand- 
est spectacles at sea is offered by these regular movements of the waves 
in perfectly calm weather, when not a breath stirs the sails ; high, blue, 
and foamless, the liquid masses succeed one another at intervals of 200 
to 300 yards, pass under the ship in silence, and, pursued by other waves, 
are lost in the far distance. One contemplates with a feeling of admi- 
ration, not unmixed with terror, the calm and majestic wave advancing 
like a moving rampart, as if about to swallow up all before it, "and ^^et 
hardly leaving a sign to mark its passage. These waves appear with 
surprising regularity during the autumnal calms, under the Tropic of 
Cancer, and almost at every season in the narrower part of the Carib- 
bean Sea toward the Gulf of Darien ; there the waves are seen silently 
to advance, and slightly raise the ship, passing onward Avith scarcely a 
murmur, as regularly as the furrows of a field, and stretching as far as 
the eye can see. 

Such perfectly regular waves .as these can only be formed in seas ex- 
posed to the influence of equable winds, such as the trade-winds. Wher- 
ever the winds are uncertain and shifty, blowing in gusts, it is evident 
that the waves driven by them can not assume a regular form or follow 
in a uniform direction. For aerial currents constantly vary in their 
speed ; being composed of strata of unequal force, which, moving at a 
rate different from that of the surface of the sea, alternately increase and 
diminish in force. Under the influence of these variable atmospheric im- 
pulses, the waves must necessarily vary in height and speed, and their 



60 



THE OCEAN. 



crests can not be developed in a vinifovm line. The wind also frequently 
changes its direction ; as if urged by some new impulse,* it commences 
blowing from another point of the compass, and drives the waves in a 
different direction from that Avhich it had- itself given them. Neverthe- 
less, the first movement is continued by the succeeding waves even while 
the second is still making itself felt, and from this double impulse an in- 
tersection of waves, differing from one another in direction, height, and 
speed, results. Let the wind shift to another point of the compass, and 
a third undulation crosses the preceding two. Finally, should the aerial 
current make the complete circuit of the compass, the ripples of the wa- 
ter pursue one another in all directions, urged from all points of the im- 
mense circle. Not a breath is lost on the sensitive surface of the sea, 
and the variety of its undulations testifies to the diversity of the aerial 
movements which cause them. 

From a lofty Ijeadland or from the mast of a ship, whence a vast ex- 
panse of water can be viewed, the beautiful sight may be often enjoyed 
of two or three systems of waves intersecting each other at various an- 
gles. Now they double the natural height of the undulations, by piling 
one wave upon another, and then again they equalize the surface of the 
water by throwing billows into the furrows. Sometimes the sea is so 
agitated that it is impossible to discern the direction of all the waves 
which have aided in producing the violent commotion. As to the voy- 
agers, whom the wave-tossed ship incessantly shakes by its rolling and 
pitching, it is still more difiicult for them to recognize in the intersection 
of the waves the various impulses communicated to the sea by the at- 

Prow. 




Stern. 
. 18.— Rollings of a Ship upon the Waves. 



mosphere. The accompanying figure is reproduced from that of an En- 
glish traveler, of the curves drawn during a single minute by a pencil 
* See below, the chapter entitled The Air and the Wind. 



HEIGHT OF WAVES. 



61 



suspended, vertically in the cabin of a sliip. At the time when the pen- 
cil traced these lines, the wind was low and tlie motion of the water 
very moderate. 

The height of the waves is not the same in all seas ; it is greater when 
the basin is deeper in proj^ortion to the exposure of its surface to the 
wind, and also in proportion as the water, being less salt and so lighter, 
yields more readily to the atmospheric curi-ents. Thus, assuming equali- 
ty of surface, the water of Lake Superior would be raised in higher 
waves than that of a gulf of the sea barred on tlie open side by islands 
and sand-banks. When of equal saltness, the narrowest basins ought to 
present the shortest and least elevated waves. The waves of the Cas- 
' pian Sea are not to be comj^ared Avith those of the Mediten-anean, which, 
again, are greatly exceeded in height by those of the North Atlantic ; 
and these latter, in their turn, ai'e surpassed by those of the Antarctic 
Sea, AvhiCh spreads over an entire hemisphere. 

According to Admiral Smyth, who was well acquainted with the Med- 
iterranean, the tempest waves rise from 13 to 18 feet in vertical height 
above the trough of the sea. He has even seen quite exceptional waves 
rise to the height of above 30 feet, but the average waves raised by high 
winds were only from about 10 to 13 feet.* In one passage from Liver-, 
pool to Boston, Avhich the celebrated navigator Scoresby made in 1847, 
he measured waves from 26 to 2^^ feet, and the average of all his obser- 
vations gave a height of about 19 feet for the largest waves. Oh his 
return in 1848, he fouitd the average to be 30 .feet, and some among the 
waves he measured rose to about 43 feet above the trouo-h of the sea. 



JaimaryretouigylVlarch Aprfl Mixy Jmie Jiily An^st Sept^?'' Oct^P Nov^?'' Deo''?^ 




Fig. 19.— Average Heights of Waves observed at Lybster (Scotland) iu 1S52. 



Other navigators have given similar estimates for the highest crests of 
waves in the North Atlantic ; but the mean elevation is much less. One 
can form a good notion by the preceding diagram, drawn by the engineer 
Middlemiss to represent the annual variations of the wave at Lybster, on 
the coast of Scotland. 

In the South Atlantic the height of the waves is certainly greater than 
* Cialdi, Sul Moto Ondoso del Mare, p. 142. 



62 THE OCEAN. 

in the northern parts. Many seainen have seen the water rise to be- 
tween 50 and 60 feet oif the Cape of Good Hope, where the basins of 
the Atlantic and the Indian Oceans meet. Dumont d'Urville even as- 
serts that he has seen waves above 108 feet high, to the depths of which 
the ship descended as into a valley, and M. Fleuriot de Langle attests 
the truth of this assertion. These are, indeed, the mountains of which 
poets speak, and wliich, in fact, seem such to those who find themselves 
at their mercy. It is probable, too, that the highest waves of the sea 
have not yet been measured. One remarkable thing is, that it is not 
usually during the most violent tempests that the hugest waves are* 
formed. On the contrary, the force of the atmosphere which then pre- 
cipitates itself obliquely on the waves, so to speak, dejjresses and crushes ' 
them.* 

The waves are developed in all their majesty when the wind is at the 
same time very high and very regular, and blows for a long time from 
the same point of the compass. 




Fig. 20. — Average Amplitude of Waves. 

As to the width of the waves — that is to say, their total breadth, from 
base *to base — observens have not obtained the same results ; but there 
ai"e few among them who have found the verticaWieight of the crest of 
the wave to be less than a twentieth or more than a tenth of the width. 
On an average the height oi' an undulation of the water is only equal to 
the fifteenth part of its base ; thus a wave of 4 feet in height measures 
40 feet from valley to valley, and a wave 33 feet high is 495 feet in 
width. This is a much smaller size than would be imagined by the sail- 
or lost in the midst of the billows, which he sees rising around him in 
every direction. Moreover, the inclination of the waves varies with the 
force of the wind, and the movements of the secondaiy undulations which 
intersect the principal ones. 

The speed of the waves is only an apparent speed, like that of the folds 
of a cloth raised by a current of air. Thus, although the water pressed 
by the wind rises and sinks by turns, it nevertheless hardly changes its 
place, and objects floating on its surface move but slowly and in an un- 
dulatory mannei". The real movement of the 'sea is that of a drifting 
current which gradually forms under the prolonged action of the wind ; 
but this general movement of the liquid mass is, after all, inconsiderable. 
The only part which advances with the storni is the foaming crest which, 
curling over the summit of the waves, dashes down the slope in front. 
By their incessant movements, the surface of the waves gradually increase 
in temperature, as has been observed after a succession of violent storms.f 

* Cialdi, Sul Moto Ondoso del Mare, p. 139. 

t Joule. Cialdi, Sul Moto Ondoso del Mare, p. 218. 



DEPTH OF MOVING WAVE. 63 

The apparent displacement of the billows (which is rather difficult to 
measure with exactitude in the open sea) varies in a regular manner, 
according to the magnitude of its waves and the depth of its waters. 
Thus, according to the calculations of the astronomer Airey, every Avave 
of 100 feet in width, traversing a sea of 164 fathoms mean depth, has a 
velocity of nearly 2100 feet per second, or about 15^ miles per hour; a 
wave of 674 feet, moving over the surface of a sea 1640 fathoms deep, 
travels more than 69 feet per second, or nearly 50 miles per hour; this 
last figure may be considered as an average speed for storm-waves in 
great seas. Since, therefore, we can by calculation infer the velocity of 
waves from their width and the known depth of the ocean-bed, it is easy 
to determine by an inverse opevation what is the ,depth of the ocean it- 
self, provided that we know the rate of motion of the waves. It is by 
this method that the mean depths of the South Atlantic and of the Pa- 
cific Ocean, between Japan and California, have been calculated,* 

Natural philosophers have frequently discussed the question of the 
movement of the waves in a vertical direction. To Avhat depth in the 
abysses of the sea does the action of the superficial wave penetrate, and 
at how many fathoms can it disturb the sand and debris at the bottom? 
It was formerly admitted, as a well-ascertained fact, but Avitliout jjroof, 
that the agitation of the sea ceases to be felt at four to six fathoms below 
the surface. Direct observations made by seamen in many latitudes 
have shown that this opinion is erroneous. Sailors have frequently seen 
the waves break at 10, 16, and even 27 fathoms of depth over hidden 
rocks, which proves that the rocks were obstacles which abruptly barred 
the advance of the lowest part of the wave. Still more frequently, dur- 
ing violent tempests, the water has been seen charged with clay and 
mud, which had been raised from the bottom at 50, 80, and even 100 
fathoms below the surface.f The direct experiments of Weber on the 
movements of waves have likewise proved that each wave extends its in- 
fluence in a vertical direction to 350 times its height. Thus every wave 
of about a foot in height makes itself felt on the bed of the North Sea at 
a depth of 50 fathoms; while every oceanic billow of 33 feet is felt at 
about If miles. It is true that at these enormous depths the action of 
the wave is, so to speak, imaginary, for below the surface it decreases in 
geometrical proportion ; but at about 25 to 50 fathoms only, the subma- 
rine waves have still great force, and we can easily understand that 
when thousands of them are abruptly arrested by submarine rocks, and 
on the rapid slopes of sand-banks, violent eddies must be produced which, 
afterwai'd returning to the surface of the water, cause " heavy swells," 
From these causes arise those turbulent seas which ships encounter at 
times in calm weather, especially in the neighborhood of submarine 
banks; also those "ground swells" which suddenly raise the surface of 
the sea and endanger boats; and those formidable tide- races which, 

I 

. * See above, p. 30. 

+ Cialdi, Sul Moto Ondoso del Mare, p. 174. 



64 THE OCEAN. 

springing from the depths of the ocean, advance abi'uj)tly upon its slop- 
ing beaches, destroying all they encounter on their way. 

It is along the shgres of continents and around rocky islands that ordi- 
nary waves and heavy surf appear in all their grandeur and assume di- 
mensions truly formidable. In accordance with the more or less gradual 
inclination of the bottom to the shore, a wave coming from the open sea 
rolls over a bed more and more shallow, and must perforce slacken its 
speed ; but at the same time, it increases by its own depth the stratum 
of water which it overflows, and consequently the wave which follows it 
is subjected to less retardation of the impulsive force. The second wave 
constantly gains on the first, and finally reaches it, swelling its crest, and, 
slackening its own speed in its turn, gives a third wave time to distance 
it also. Finally, near the strand, the liquid mass, swelled by the pursuing 
waves, and unable to spread out farther at its base along the shore, which 
is too near, gains in height what it wants in breadth, and, rising like a 
wall, it bends over with a wide curve in front, and breaks with a thun- 
dering sound, throwing water, mixed with sand and foam, far along the 
shore. This surge, which is dreadful indeed during tempests, rises much 
higher than the waves ; to the ancients the whitening billows of the open 
sea, whose crests were seen to shine like the fleeces of sheep, were the 
flocks of Proteus ; while the waves of the shore, still called in our days 
cavalli and cavalloni by the peojale of the south of Europe, were the 
foaming horses of Neptune. 

The lieight to which the crests of some of these waves attain when the 
configuration of the coast favors the movement, seems sometimes to par- 
take of the marvelous. The mass of water which rises vertically can 
then only be compared to an ascending cataract. Spallanzani relates 
that sometimes, in violent tempests, the waves reach half-way up, or even 
to the top, of Stromboluzzo, a peak of lava which rises near Stromboli, 
318 feet above the mean level of the sea. The Bell Rock light-house, 
which rises boldly to 112 feet in height on a rock ofl" the Scottish coast, 
is often enveloped in waves and foam even long after the tempest has 
ceased to disturb the sea.* Smeaton, too, has seen waves covering the 
Eddystone light-house, and leaping in a spout of water 82 feet above the 
lantern ; the mass which is thus raised around the edifice can not be less 
than from 2616 to 3924 cubic yards, and would weigh as much as a large 
three-decker. After these great storms, salt pools are scattered here and 
there on the top of the clifis. 

The pressure exerted by these masses of water, hurled with such impe- 
tus, is no less surprising. Thomas Stephenson ascertained that the force 
of the sea dashed against the. Bell Rock light-house amounted to about 
17 tons for every square yard. In the Island of Skerryvore the heaviest 
calculated pressure is about three tons and a half for every yard — that is 
to say, more than Q^ lbs. avoirdupois for every 0*16 of a square inch. 
With such a force the displacement of blocks which seem enormous to u# 
* Mrs. Somerville, Physical Geography. 



FORCE OF THE WAVES. 



65 



is only child's play to the tempest waves. Before all sea-ports and road- 
steads where great works, such as sea-walls and breakwaters, have been 
constructed, seamen have been able to observe the prodigious power of 
the angry water. On all the exposed works at Holyhead, Kingston, 
Portland, Cherbourg, Port Vendres, Leghorn, the waves have been seen to 
seize blocks weighing several tons, and hurl them like playthings over 
the dikes. At Cherbourg the heaviest cannon on the rampart have been 
displaced ; at Barra Head, in the Hebrides, Thomas Stephenson states 
that a block of stone of 43 tons was driven more than If yards by the 
breakers. At Plymouth, a vessel weighing 200 tons was thrown, with- 
out being broken, to the very top of the dike, where it remained erect as 
on a shelf beyond the fury of the waves. At Dunkirk, M. Villarceau has 
ascertained, by the most delicate measurements, that during a heavy sea 
the ground trembles at nearly one mile from the shore. 




Fig. 21.— Bay of St. Jean de Luz. 
5 



66 THE OCEAN. 

In the Gulf of Gascony, so frequently visited by tempests, the waves, 
coming from the west and north-west, are drawn into a sort of funnel, and 
hurl themselves against the shores with a force at least equal to that of 
the waves in the Channel and the English seas. The works constructed 
by engineers to protect the roads and ports against this terrible pressure 
have been frequently swept away, or much damaged by the waves. Man 
must incessantly continue the strife he is engaged in with the sea, tinder 
pain of seeing the work of a century destroyed in a day. During the 
winter of 1867 and 1868, M. Palaa says that blocks of masonry, 36 tons 
in weight, placed at the extremity of the dike at Biarritz, were thrown 
horizontally from 11 to 13 yards ; one block was even raised nearly seven 
feet, carried over the breakwater, then thrown down, and rolled to a great 
distance during the storm. At St. Jean de Luz the surge is perhaps still 
mor^ terrible, and some of the masses of stone now employed in con- 
structing the dike of Socoa, at the entrance to the roadstead, are not' less 
than from 80 to 90 cubic yards. And yet even this strong wall would 
not be strong enough, if it was not additionally defended by stones scat- 
tered loosely here and there, forming a range of protecting rocks in front 
of the dike upon which the sea expends its fury. 

The only places where the waves display a still greater power than in 
the Gulf of Gascony are those that are sometimes ravaged by the torna- 
does. In the Isle of Reunion there is to be found in the middle of a sa- 
vanna a massive block of madrej^oric stone, which is no less than 510 cu- 
bic yards in size. It is a piece that the waves' have detached from a 
reef and driven before them across the land.* How can we wonder that 
waves strong enough to hurl such projectiles can alter the shores in such 
varied ways, demolishing the cliffs here, and forming islands there, or con- 
structing sand-banks at the entrances to gulfs.f 

* Zurchei- and Margolle. 

t See the chapters entitled The Shores and the Islands ; the Work of Man. 



GENERAL CAUSES OF CURRENTS. 



67 



I 



BOOK II.— CURRENTS. 



CHAPTER VII. 

GREAT MOVEMENTS OF THE SEA. — GENERAL CAUSES OF CURRENTS. — THE 
FIVE OCEANIC RIVERS. 

Currents, that is to say, the real movements of the sea, much less 
visible to the eye than the apparent displacements which constitute the 
waves, are notwithstanding of much greater importance in the economy 
of our planet. By their action enormous volumes of water, thousands of 
miles wide and hundreds of fathoms deep, move across the oceanic ba- 
sins; the water of the polar seas is carried to equatorial regions, while 
these, on their side, send, their waves in the direction of the poles. The 
liquid mass circulates incessantly, as if in a vast whirlpool, in every ocean 
of the globe, and we can follow in thought its gigantic circuit from the 
fields of ice to the warm atraosjihere of the tropics. Currents are indeed 
only the ocean itself in luotion, and by their action the waters of the sea 
are successively distributed over all parts of the globe. They are the 
windings of the great " salt river " of Homer, which rolls around the 
earth in one immense circuit. Every drop that has not already been 
raised in vapor to commence its long journey through clouds, mists, 
glaciers, and rivers, continually changes its place in the abysses of the 
sea ; it descends to the bottom, or mounts to the surface ; it moves from 
the equator to the pole, or from the pole to the equator ; and thus trav- 
erses all parts of the ocean. It is to this continual displacerdent of its 
innumerable particles that the sea owes its unifofmity in such a surpris- 
ing manner, under all latitudes, as regards the appearance, composition, 
and saltness of its waters. 

Every difference of level which is jiroduced on the liquid surface in 
consequence of prolonged winds, heavy rains, or very active evaporation, 
causes, as a necessary result, the formation of a current ; for water, wheth- 
er salt or fresh, ever seeks its level, and incessantly flows from the more 
elevated places toward the depressions. Every atmospheric variation 
lias, for result, a displacement in one direction or another of the superfi- 
cial water. But the great currents which flow with a regular movement 
around the basins of the ocean-, between the polar and the equatorial 
zones, are determined by general causes acting at the same time on the 
entire planet. These causes are the sun's heat and the rotation of the 
earth on its axis. 

The equatorial basin, incessantly heated by the solar rays, loses a great 



68 THE OCEAN. 

quantity of water, which is transformed into vapor, and rises into the 
higher strata of the atmosphere to be condensed into clouds. Admitting 
that the annual evaporation is about fourteen feet,* which is probably 
below the reality, the quantity of fluid raised from the Atlantic in the 
tropical zone would be nearly 120 trillions of cubic yards, and would con- 
sequently represent the same value as a cubic mass of water nearly 30 
miles in extent. It is true that a considerable part of this vapor, the 
half perhaps, falls as rain into the sea from which it was taken, yet a 
great proportion of the clouds are carried by the trade- windsf and other 
aerial currents, into seas situated beyond the tropics, and over the neigh- 
boring continents. Near the equator, therefore, much more water is 
drawn from the ocean by evaporation than is returned to it by the 
clouds, and, in consequence, an immense void is formed which can only 
be filled by the waters from the polar basins, vfhere the contributions of 
snow, rain, and ice exceed the loss in vapor. This superabundant mass 
of fluid continually flows toward the basin of the torrid zone, and forms 
the two great currents, which meet one another from the opposite poles 
in the Atlantic and the Pacific, incessantly describing a regular orbit 
like the celestial bodies. But the excess of evajjoration which occurs in 
tropical waters is not the only reason of this great movement of the po- 
lar seas toward the torrid zone. The trade-winds, attracted by Jhe force 
of equatorial heat, blow incessantly in the same direction, and always 
driving the waves before them, thus accelerate the march of the oceanic 
current. 

If the mass of water which continually flows from the poles to the 
equator were exactly equal in quantity to that which is evajDorated by 
the sun's heat, the arctic currents would be arrested under the tropics, 
and no return movement would be produced toward the polar oceans. 
But the waters which flow from the north and south are always in ex- 
cess, in consequence of the continual impulse of the trade-wind ; and 
when they arrive in tropical latitudes they are influenced by a new cur- 
rent, the true cause of which is the rotation of the earth on its axis. In 
fact, owing to the incoherence of its particles, the ocean does not obey 
in an absolute manner the rotatory motion of the earth, which carries it 
from west to east. In descending from the poles to the equator, and 
thus crossing latitudes whose speed of rotation is greater than their own, 
they are constantly drawn obliquely toward the west, and this continual 
retardation of their motion behind that of the rotation of the globe be- 
comes, in relation to the surface of the sea, an apparent motion from east 
to west. Upon their meeting in the tropics, the polar currents, being both 
afifected by a side movement, strike each other obliquely, then reunite in 
the same oceanic river, and flow directly toward the west in the opposite 
direction to that of the solid earth. It is thus that the equatorial cur- 
rent is produced, which, with the two polar currents, determines all the 

* Mauiy's Geography of the Sea. 

t See the chapter entitled The Air and the Winds. 



THE OCEANIC RIVEBS. gg 

movements of the waters in each oceanic basin. The other rivers of the 
sea are simply branches from them, caused by the form of the continents. 
The equatorial current, which is a continuation of the polar currents, 
and forms with them a vast semicircle, can not be freely develojDed 
around the circumference of the globe. Arrested in the Atlantic by the 
American continent, in the Pacific by Asia and the archipelago which 
unites that continent with New Holland, it breaks against the shores 
and divides into two halves, which flow back in the direction of the poles, 
the one descending toward the south, the other ascending to the north. 
The immense river thus returns to its source, but at the same time the 
motion of terrestrial rotation, which at its outset caused it incessantly to 
deviate toward the west, now urges it obliquely in the opposite direction. 
Under the equator, the angular speed of the terrestrial surface around 
the axis of the planet being much more considerable than under any oth- 
er latitude, the waters coming from the tropics into temperate seas are 
animated by a more rapid movement toward the east than those amidst 
which they flow. They deviate in consequence in an easterly direction, 
and when the returning current reaches the polar sea it seems to come 
from the west. Thus the grand circuit of the waters is completed in 
each hemisphere. The Atlantic and the Pacific have each their double 
circulatory system, formed of two immense eddies united in the torrid 
zone by a common equatorial current. As regai'ds the Indian Ocean, be- 
ing bounded on the north by the continent of Asia, it has but one simple 
current, which turns incessantly in its vast basin between Australia and 
Africa. As a whole, these ocean rivers recall, by their distribution, the 
divisions of the land. The two great whirlpools of the Atlantic corre- 
spond to the two continents of Europe and Africa; the huge eddies of the 
Pacific have a binary division analogous to the two continents of Ameri- 
ca; and the current of the Indian Ocean reminds one of the enormous 
mass of Asia, which alone fills half the northern hemisphere. 



70 THE OCEAN. 



CHAPTER VIII. 

THE GULF STEEAM. — INFLUENCE OP THIS CURRENT ON CLIMATE. — ITS IM- 
PORTANCE TO COMMERCE. 

Of all the oceanic rivers, the best known to us is that part of the North 
Atlantic current which the English and the Americans have named the 
Gulf Stream, because it makes a long circuit in the Gulf of Mexico before 
reaching the ocean. In the year 1513 the Spaniards, Ponce de Leon and 
Antonio de Alaminos, knew of the existence of this current; and six years 
later Alaminos, setting forth from the Straits of Florida, allowed himself to 
be carried by the water into the open sea, and thus discovered the great 
circular route which ships have now to follow in order to return speedily 
to Europe. Since the time of Varenius, who attempted to describe the 
Gulf Stream, of Vossius, who traced its immense circuit on a map, Frank- 
lin 'and Blagden, who were the first to explore it scientifically, this cur- 
rent has been studied by numerous geographers. Without doubt, there 
is no marine current which merits to be better known in all its details; 
none has been of more importance in the commerce of nations or exercises 
a greater influence upon the climate of the north-west of Europe. It is 
to the Gulf Stream that the British Isles, France, and the neighboring- 
countries owe in great part their mild temperature, their agricultural 
wealth, and, in consequence, a very considerable part of their material and 
moral power.* . Its history is almost identical with that of the entire 
North Atlantic Ocean, so important is its hydrological and climatic in- 
fluence.! 

The celebrated Maury devotes the most important part of his classical 
woi'k on the " Geography of the Sea " to the Gulf Stream. It " is a river 
in the ocean ; in the severest droughts it never fails, in the mightiest 
floods it never overflows. Its banks and its bottom are of cold water, 
while its current is of warm. There is in the world no other such ma- 
jestic flow of waters. Its current is more rapid than the Mississippi or 
the Amazon, and its volume a thousand times greater." Such is the epic 
language in which Maury's fine work commences.^ 

After having made the tour of the Caribbean Sea and the Gulf of Mex- 
ico in six months, after having driven back upon the shores of Alabama 
the muddy waters of the Mississippi which border its dark blue waves, 
the Gulf Stream follows the northern coasts of Cuba, then turns the 
southern point of Florida, and penetrates the strait which separates the 
American continent from the islands and banks of Bahama. Swelled by 

* See the chapter entitled The Earth and Man, 
t J. G. Kohl, Geschichte des Golfstroms, p. 1. 
I Physical Geography of the Sea, p. 23. 



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•S. l^EW YORK 



COURSE OF THE GULP STREAM. 71 

the mass of water Avhich.the great equatorial current sends directly 
through the straits of the archipelago, and above all by the old channel 
of Bahama, the Gulf Stream flows straight to the north, pressing througli 
the ocean like a river nearly 37 miles wide, and of an average depth of 
200 fathoms. Its speed is great, even equaling that of the principal riv- 
ers of the world, being sometimes from about 4^ to 5 miles an hour; but 
usually it is about 3|^ miles. The mass of water discharged by the cur- 
rent may, therefore, be estimated at nearly 45 millions of cubic yards per 
second — that is to say, at 2000 times the mean discharge of the Missis- 
sippi; and yet it was to tlje outflow of this North American river that 
many geographers formerly attributed the existence of the Gulf Stream ! 
When winds from the south, the west, or even the north-west, Snd the 
movement of the tides, favor the progress of this current, it rolls toward 
the Atlantic in much greater volume than usual. But on the other hand, 
when retarded by tempests that blow from the north-east, it pours a 
much smaller quantity of water into the ocean. When thus checked, it 
swells, rises, spreads with fury over the low lands that border it, ravages 
vast tracts, and causes whole islands to disappear. At its embouchure 
into the ocean, this marine river resembles those sti'eams which flow 
through, continents, it erodes on the one side, while it deposits alluvium 
on the other. And doubtless the Bahama Islands, which are scattered 
through the sea to the east of the Gulf Stream, and the keys or rocks de- 
veloped on the north in a long range, rest on a foundation of submarine 
banks formed in part by the deposits of this gi-and river.* 

On emerging from the Strait of Bemini, the Gulf Stream expands and 
spreads over the Atlantic, but at the same time its depth becomes pro- 
portionately less considerable. While the strata of cold water which 
serve as its banks'retire on each side and allow it to spread over a great- 
er breadth, the bed of cold water which bears it and over which it flows, 
as terrestrial rivers glide over beds of rocks, gradually approaches near- 
er the surface. At Cape Hatteras the depth of the current is about 120 
fathoms, and its speed does not exceed three miles per hour; but it is 
twice as wide when it emerges from the Strait of Bemini, and spreads 
over a space of about 78 miles. The thickness of this powerful stream 
of warm water is constantly diminishing, and when it has crossed the At- 
lantic it is only a superficial sheet. But even then it covers an immense 
extent, reaching from the Azores to Iceland and Spitzbergen, 

The soundings taken since 1845 by the ofiicers of the Coast Surve}'- of 
North America prove that the Gulf Stream flows along the coast of the 
United States at some distance from the land. The slight inclination of 
the low lands of Georgia and Carolina is continued under water till the 
lead reaches a depth of about 50 fathoms. The bottom then sinks rapid- 
ly, and forms a long valley parallel to the shore of the United States and 
the chalky walls of the Appalachians; it is in this valley, hollowed to 

* Agassiz. E. Thoraassy, Bulletin de la Societe de Geographie, Noverabre, 1860. See 
the chapter entitled Earth and its Fauna. 



72 



THE OCEAN. 




The Soundings are in fathoms. 
Fig. 22.— Channel of Florida. 

the east of the sulbmarine basement of America, that the waters of the 
Gulf Stream flow. Owing to the rotatory motion of the globe, and prob- 
ably also to the general direction of the coasts, the current follows a con- 
stant direction to the north-east, and does not touch any of the advanced 
points of the continent. Off New York and Cape Cod it deviates more 
and more to the east, and, ceasing to follow at a distance the American 



MEETING OF HOT AND COLD CURRENTS. . 73 

coast-line, rolls across the open Atlantic toward the shores of "Western 
Europe. Thus, as Maury says, if an enormous cannon had force enough 
to send a bullet from the strait of the Bahamas to the North Pole, the 
projectile would follow almost exactly the curve of the Gulf Stream, and, 
gradually deviating on its way, Avould reach Europe from the west. 

Between the 43d and 47th degrees of north latitude, in the neighbor- 
hood of the Banks of Newfoundland, the Gulf Stream, coming from the 
south-west, meets on the surface of the sea the polar current discovered 
by Cabot in the year 1497. The line of demarkation between these two 
oceanic rivers is never absolutely constant, but varies with the seasons. 
In winter — that is to say, from September to March — the cold current 
drives the Gulf Stream toward the south ; for during this season all the 
circulatory system of the Atlantic, winds, rains, and currents, approach 
more nearly the southern hemisphere, above which the sun travels. In 
summer — that is to say, from March to September — the Gulf Stream, in 
its turn, resumes its preponderance, and forces back the line of its conflict 
with the polar current more and more toward the north. Thus the great 
river undulates here and there over the seas, and, according to the grace- 
ful expression of Maury, waves like a pennon in the breeze. But it is 
probable that the advance of the two opposing currents is often modified 
only in appearance, in consequence of the superficial expansion of cold or 
warm water. The Banks of Newfoundland, that enormous plateau sur- 
rounded on all sides by abysses five to six miles deep, is undoubtedly 
due in great part to the meeting of these two moving liquid masses. On 
entering the tepid waters of the Gulf Stream, the icebergs gradually melt 
and let fall the fragments of rock and loads of earth which they bear 
into the sea. The bank, which rises gradually from the bottom of the 
ocean, is a sort of common moraine for the glaciers of Greenland and the 
polar archipelago.* 

After encountering the waters of the Gulf Stream, those of the Arctic 
current cease in great part to flow on the surface, and descend into the 
depths, in consequence of the greater weight which their low tempera- 
ture gives them. The direction of this counter-current, exactly opposite 
to that of the Gulf Stream, is demonstrated by the icebergs which the 
warm breath of temperate latitudes has not yet melted, which travel 
toward the south-east, directly against the superficial current, which they 
divide like the prow of a ship. More to the south, we recognize the ex- 
istence of this concealed current only by means of sounding apparatus, 
the cold waters serving as a bed to the warm river flowing from the 
Gulf of Mexico ; it descends lower and lower as far as the Straits of Ba- 
hama, where the thei'mometer discovers it at a depth of 220 fathoms. 

Nevertheless, a part of the waters of the polar current remains at the 
surface of the sea ; and, gliding along the western coasts of the United 
States as far as the point of Florida, gives to the Gulf Stream, by contrast, 
very sharply defined limits. Generally the cold water coming from the 

* See above, p. 29. 



'74 • THE OCEAN. 

Arctic" Sea possesses sufficient force to compel the current from the Gulf 
to bend sensibly toward the south, and to oppose an insurmountable bar- 
rier to it in the other direction. The warmest and most rapid part of 
the Gulf Stream, which forms precisely the left or western side of the cur- 
I'ent, is found in immediate juxtaposition to a sheet of cold water, which 
spreads in an opposite direction between the Gulf Stream and the Ameri- 
can shores. This counter-current, which interposes the waters of the Icy 
Sea between the coast of Carolina and the warm i-iver flowing from the 
Gulf of Mexico, bounds the Gulf Stream like a wall of ice.* Sometimes 
the line of demarkation between the two liquid masses is so precise that 
it is appreciable to the sight, and the exact moment when a ship leaves 
one current, to cleave the other with its prow, may be distinguished. 
The water of the Gulf Stream is of a beautiful azure, that of the counter- 
current is greenish ; the first is saturated with salt, the latter contains it 
in a much less proportion. The one is tepid, the other cold; and the ther- 
mometer, when plunged alternately in the two liquids, instantly marks 
the difference of temperature. On the boundary line of the currents, the 
friction of the two masses of water flowing in opposite directions pro- 
duces a series of eddies, whirlpools, and short waves, which give to these 
ocean rivers an aspect similar to that of continental rivers. Sometimes 
one can even hear, like a dull roaring, the noise of the waters contending 
on the surface of the sea. Floating plants and other fragments are whirl- 
ed round on the ever-changing boundary of the two contending streams.f 

The GulftStream, like all other currents, finally mingles with the sea, 
and thus tends to equalize the proportion of salt and all other substances 
contained in the liquid mass. The normal salinity of the Caribbean Sea 
is from 36 to 37 thousandths, except in the neighborhood of the mouths 
of great rivers. After having received the fresh waters of the Missis- 
sippi and the visible and subterranean rivers of Florida, the Gulf Stream 
does not contain quite 36 thousandths of saline substances ; but this is 
gradually increased as it advances toward the north. Off Newfound- 
land, where the waters of the St. Lawrence and many other rivers, as 
well as the melted ice, fogs, and heavy rains, have rendered the waves of 
the sea more fresh, the Gulf Stream contains less than 34 parts in 1000 
of saline matter, but it gradually increases the proportion to 35 thou- 
sandths as it shapes its course toward the coasts of Western Europe and 
the polar regions. The currents of cold water which serve as its bed are 
all less rich in saline substances, as Forchhammer and other chemists 
have proved. But in consequence of the incessant mixture of the waters, 
an equalization of saltness between the currents is produced in the vari- 
ous latitudes.^ 

Another effect of the Gulf Stream, no less important in the economy of 
our planet, is that which it accomplishes, in concert with the south-west 

* Franklin Bache, United States Coast-Survey. 

t Kohl ; Fitzroy, Adventure and Beagle, Appendix to vol. ii. 

X Forchhammer, Philosophical Transactions, part i., p. 241, 1865. 



EFFECT OF THE GULF STREAM ON CLIMATE. 75 

winds,* on the climate of Western Europe. While rotating in the Gulf 
of Mexico as in an immense caldron, the waters of the current are gradu- 
ally heated : when they escape through the Strait of Bernini to enter the 
ocean, their temperature is not Jess than 86° Falir,, and exceeds by about 
4° Fahr. the natural heat of the neighboring beds of water. The waters 
of the Gulf Stream lose their warmth but slowly, and during winter they 
often have, oft' Cape Hatteras and the Banks of Newfoundland, a temper- 
ature exceeding by 21° or 28° Fahr. that of the rest of the Atlantic un- 
der the same latitudes. When the Gulf Stream meets the polar current, 
the former has still a temperature of 36° or even 45° Fahr., while, even 
at a distance of some hundreds of miles from the coasts of Labrador, the 
latter is sometimes found to be below freezing-point (24'8° Fahr.) ; thus, 
in defiance of latitude, the waters of the tropics and of the icy zone are 
brought into juxtaposition. In its advance toward the north, the up- 
per strata, which in consequence of radiation have become colder than 
the subjacent layers, descend to a greater or less depth in the mass of 
the current, and are replaced by the warmer and lighter water lying im- 
mediately below. Thus a constant alternation of position is produced in 
the liquid strata of the Gulf Stream, and one may remark in consequence, 
in crossing the whole breadth of the current, a series of parallel bands of 
unequal temperature. f In each of these bands the warm water rises by 
turns to the chilled surface of the sea. It is a remarkable fact, that if the 
Gulf Stream did not flow as it does in a bed entirely composed of cold 
water, but moved along the very bottom of the ocean, it would rapidly 
lose its high temperature, and would cease in consequence to be a source 
of heat for Western Europe. In fact, the earth being a better conductor 
of heat than the water, the warm waters of the current would communi- 
cate their temperature to it, and would finally lose their whole store. 
But the cold waters of the polar current, being interposed between the 
bottom of the sea and the waters of the Gulf Stream, serve as a protect- 
ing screen to the latter, and hinder their refrigeration. It is by such con- 
trasts as these that the harmony of the world is established. 

The qua\itity of heat which the Gulf Stream carries toward the north- 
ern regions forms a very considerable part of the caloric stored up in its 
waters under the tropics. The cetaceans, fish, and other inhabitants of 
the torrid zone follow the course of the Gulf Stream without perceiving 
that they have changed their country, and often push their adventurous 
voyages to the Azores, and even to the coasts of Iceland ; the southern 
birds mount also toward the north in the warm stream of air reposing on 
the current. The animals of northern seas, on the contrary, are kept 
• prisoners in the glacial ocean, and the right whales, says Mauiy, recoil 
before the Gulf Stream as before " a barrier of flame." The total warmth 
of the current would suflice, if it was centred in a single point, to fuse 
mountains of iron, and cause a river of metal as mighty as the Mississippi 

* See the chapter entitled Climates. 

t Franklin Bache, United States Coast-Survey. 



76 THE OCEAN. 

to flow forth. It would sufiice also to raise from a winter to a constant 
summer temperature the entire column of air which rests on France and 
the British Isles. But though it is spread over enormous spaces to the 
west and north of Europe, the Gulf Stream does nevertkeless exercise a 
preponderating influence upon the climate of this part of the Old World. 
Owing to the warmth of its waters, the lakes of the Faroe and Shetland 
Isles never freeze during winter; Great Britain is enveloped in fogs as 
in an immense vapor-bath, and the myrtle grows on the shores of Ireland, 
the " emerald isle of the seas," under the same latitude as Labrador, that 
land of snow and ice. In green Erin, an island privileged in so many re- 
spects, the western coasts (the first land which the Gulf Stream encoun- 
ters after crossing the Atlantic) enjoy a temperature two degrees higher 
than that of the eastern coasts. In spite of the path of the sun, it is, on 
an average, as warm in Ireland under the 52d degree of latitude as in 
the United States under the 38th degree, or about 1025 miles nearer the 
equator. 

The Gulf Stream, which conveys the troj)ical warmth to the temper- 
ate countries of Europe, very often serves as a high-road for tempests. 
Hence the names of loeather-hreeder and storm-king, which have been 
given to this current.* The movements of the atmospheric ocean and 
those of the ocean of waters occur in such complete parallelism -that one 
would be tempted to regard them as one and the same phenomenon in 
the ensemble of aerial and nlarine currents.f Thus the Gulf Stream 
seems to be for the winds, as it really is for the waters, the great medium 
between the Old and New Worlds. It carries to the seas at the north 
of Europe the salinity of the Gulf of Mexico ; it bears wnth it the warmth 
of the tropics for the advantage of the temperate regions, and marks the 
track which the torrents of electricity, disengaged by the hurricanes of 
the Antilles, follow. It is, indeed, the great serpent of the Scandinavian 
poets, which uncoils its immense folds across the ocean, and from its head, 
which it waves here and there over the shores, wafts a gentle breeze, or 
pours forth storm and lightning. 

The Gulf Stream crosses the Atlantic with a mean speed of aboiit 24 
miles a day, as has been ascertained either by direct measurement at dif- 
ferent parts of the ocean or by means of notes, which, having been thrown 
overboard in bottles carefully closed, have floated for weeks or months 
at the will of the waves, and then been fished up in other latitudes or 
found on some sea-shore. In their long passage, the deep waters of the 
marine river of America transport scarcely any other alluvium than the 
living frustules of animalcula, which fill the tepid waters of the current, 
and are constantly falling in a kind of snow to the bottom of the sea. 
But here and there on the surface of the Gulf Stream float trunks and 
branches of trees, which are finally thrown on some coast of Europe, and 
even on the Island of Spitzbergen. It was these remains which ^ur an- 

* r. Maury, Geography of the Sea. 

t See the chapter entitled The Air and the Winds. 



EXTENT OF THE GULF STREAM. 77 

cestors of the Middle Ages believed to come from the fabulous Island of 
St. Brandan or from Autilia, and which furnished matter for thought to 
daring navigators like the great Columbus.* Seeds carried from the 
New World by the current have found a favorable soil on the shore of 
the Azores, and, although many thousand of miles from their native land, 
have germinated and borne fruit. Often, too, the waves of the Gulf 
Stream bring to Europe the broken products of human industry and the 
timber of wrecked ships. During the Seven Years' War, the mainmast 
of an English ship of war, the Tilbury.^ which had been burned near St. 
Domingo, was found on the northern coasts of Scotland. In the same 
way a river-boat, laden with mahogany, was once even driven to the 
Faroe Islands. The remains of ships wrecked in the latitude of Guinea 
have been brought to the coast of the British Islands, after having twice 
crossed the ocean in opposite directions, and Esquimaux have often been 
carried by the waves to the Orkneys.f 

It is rather difficult to lay down the precise route of the Gulf Stream 
in the seas of Western Europe, because of the enormous width of its mov- 
ing expanse. One may say that in reality it stretches over the whole 
ocean, from the Azores to Spitzbergen ; but having lost in its onward im- 
pulse in proportion as it has gained in extent, it is modified and turned 
aside in its course by a host of local circumstances and the varied con- 
figuration of the coasts of Europe. Only that part of the current which 
flows to the north of Ireland and Great Britain maintains its original di- 
rection. It bathes all the islands between Scotland and Iceland, warms 
the coasts of Norway ; even in Lapland, it melts the ice at the port of 
Hammerfast, and then continues its course in the Polar Sea toward Spitz- 
bergen. Thus, as the Swedish expedition in 1861 ascertained, the cur- 
rent makes itself felt even on the northern shores of the latter archipela- 
go; for the seeds of a plant from the Antilles {Entada gigalohium) were 
found on the shore of Shoal Point, lying at more than 80 degrees north 
latitude. Indeed, it is certain that the current even bathes the western 
coasts of Nova Zembla, for bottles that came from a glass factory at 
Norway, and the nets of Scandinavian fishermen, have been found there. 

How, then, do these waters, which spread in such a vast sheet over the 
surface of the Icy Sea, continue their progress toward the Pole ? Here 
hypothesis commences, since no navigator has yet been able to explore 
these latitudes and study their hydrological laws. But we know at least 
in part the origin of the polar current, and by the direction which this 
mass of water takes may be indicated that which the Gulf Stream itself 
must follow. Along all the northern coasts of Siberia, as Wrangel and 
other explorers have told us, a current of cold water flows from east to 
west. Encountering on its way the large island of Nova Zembla, it 
covers the strand and rocks with enormous quantities of ice, which ren- 
der the island quite uninhabitable, and close the straits to navigation. 

* r. G. Kohl, Geschichte des Golfstroms, p. 17. 
t Humboldt, A nsichten der Natur (notes). 



78 THE OCEAN. 

Arrested by this barrier, the waters of the glacial current are forced to 
bend to the north, and flow in a north-westerly direction toward Spitz- 
bergen, round the northern archipelago of which they finally turn, in or- 
der to enter the seas around Greenland. It is here that they begin to 
take a direct road toward the equatorial seas; and all the navigators 
who have ventured to the north-west of Iceland have recognized the ex- 
istence of this stream, flowing along the coast-line as far as Cape Fare- 
well. Its average speed, according to Graah and Scoresby, is from, three 
to four miles a day. 

■ To the south of Greenland the lessened sheet of the Gulf Stream must 
meet this transverse current ; and doubtless, in consequence of the great- 
er weight which its stronger proportion of saline substances imparts to it, 
it plunges into the depths and is changed into a submarine current, which 
finishes by mixing completely with the cold waters of the northern seas, 
and flows back at last toward the equator in an opposite direction to 
that which it at first pursued. Thus the river of warm water from the 
Gulf of Mexico feeds, by its incessant contributions, the polar counter- 
current, and the great circuit is established between the zone of heat and 
that of ice. Perhaps, too, the reflux of the Gulf Stream is partially ac- 
complished, under the pressure of water from the north by an abrupt 
turn. This would explain the strong salinity of 35 thousandths, which 
Forchhammer found in the waters of the polar current to the east of 
Greenland. 

It is not only in the wide extent of the North Atlantic, from Nova 
Zembla to Iceland, that the Gulf Stream takes a submarine course ; the 
same is the case, it apj)ears, in Baffin's Bay to the west of Greenland. In 
fact, from Cape Farewell to eight degrees farther north the existence of 
a coast current has been ascertained, which carries the ice in an exactly 
contrary direction to that of the current which follows on the west the 
coasts of Labrador, and which serves as a high-road for the fragments of 
the ice-fields.* This current was formerly considered as the continuation 
of the one which flows along the eastern coast of Greenland from north 
to south, and which would thus have abruptly turned round Cape Fare- 
well. But it is much more natural to think that the polar current con- 
tinues its route directly toward the great centre in the tropical seas. In 
this case, the current on the western coast of Greenland would be simply 
a branch of the Gulf Stream, which is rendered almost certain by its 
waters being comparatively warm. The sea very seldom freezes on the 
shore which it bathes, and the climate there is on an average nine de- 
grees (Fahi-.) warmer than on the coast looking toward the east. To- 
ward the '78th degree of latitude, this river -like curi-ent completely 
ceases, and it is undoubtedly . there that it becomes submarine, perhaps 
to flow on the surface again in the open sea of Kane.f 

On the other hand, if in the icy seas the various branches of the Gulf 
Stream change into smaller counter-currents, the polar currents do the 

* See p. 52. t Graah ; Miihrj', Mittheilungen von Petermann, t. ii., 1867. 



COURSE OF THE GULF STREAM. 79 

same more to the south, and become the bed for the waters which flow 
to the north. These contain, it is true, more saline substances, but they 
are also warmer; rendered heavy by the salt, they are lightened by their 
hio-h temperature, so that a slight difference of w^armth or of salinity 
can modify their equilibrium and make them change their position with 
the polar current. In the temperate seas, where they are still warm and 
strongly saline, they flow on the surface ; but sink, on the contrary, in the 
icy seas, Avhere they are chilled, or where the admixture of Salter water is 
effected. This explains the intersection of the currents. To the north 
of Spitzbergen and Nova Zembla, the Gulf Stream is a submarine sheet ; 
to the south of Iceland, it is the waters from the pole which flow below. 
Not far from the Faroe Islands the sounding-lead can even indicate the 
direction followed by the icy counter-current, owing to the layer of vol- 
canic remains which have been brought from the coasts of Iceland, and 
spread over a space of 25 degrees of longitude between the 47th and 52d 
degree north latitude. This hidden river must flow, at least in certain 
places, on the very bottom of the sea, for various soundings taken by 
McClintock to the south-east of Iceland show that all the light detritus 
has been swept away by its waters.* 

If the Gulf Stream throws out various branches toward the north, which 
contribute to form the vast circunipolar whirlpool in the same way, an- 
other branch flowing toward the south goes to swell the eomatorial cur- 
rent. This offshoot of the Gulf Stream, of which one brauOT penetrates 
into the Bay of Biscay and forms the coast current called Rennell's,f 
flows along the coasts of the Iberian peninsula, follows the outline of 
Africa to the south of the Canaries and Cape Verd Islands, where lateral 
counter-currents occur, and enters the great marine river which moves the 
waters from east to west, " following the course of the heavens." 

Thus is completed the immense* circuit of the Atlantic, in the centre of 
which the sea-meadows of wrack| extend in clusters like an ai'chiiDelago. 
It is owing to this perpetual circuit that navigators in sailing-vessels 
have been able to reach the New World from Western Europe. If Co- 
lumbus had not made use of the semicircular current which flows from 
the coasts of Spain to the Antilles, he certainly would not have discover- 
ed America. If the pilot Alaminos, and, since his first voyage, the great- 
er part of the na«gators returning from the Antilles and United States, 
had not, either wuhout knowing it, or else well understanding the cause, 
followed the course of the Gulf Stream, the coasts of America would have 
remained practically far more distant from Europe than they really ai'e. 
The colonies, now become so prosperous as independent republics, Avould 
be still in deplorable isolation ; and civilization would have been greatly 
retarded, or even completely arrested, for want of new im^tus. As to 
commerce, properly so called, one can judge of the influence exercised 
upon it by the movement of the waters of the Atlantic, when one ex- 

* Wallich, North Atlantic Sea-bed. 

t See chapter entitled Earth and its Flora. % Ibid. 



80 



THE OCEAN. 



amines on a map the position of the great centres of trade. Havana and 
New Orleans, two principal markets of the Antilles and Mississippi States, 
are, so to say, at the source of the Gulf Stream. New York is situated 
facing the principal bend of this current, at the spot where the vast river 
flowing from the Antilles bends toward Europe. Finally, Liverpool, 
among so many other considerable ports washed by the Gulf Stream on 
its arrival at the coasts of the Old World, is the one which is most direct- 
ly in the path of its waters. 

When Franklin discovered, in 1775, that the mariner has only to plunge 
a thermometer in the water of the Atlantic to discover if he is sailing 
over the Gulf Stream or outside its course, the illustrious savant imme- 
diately perceived the importance of this fact for navigation. He even 
thought for a long time he must conceal it, from a fear that the English 
Government, then at war with the American Colonies, would profit by 
this discovery to send ships and men more rapidly against the revolted 
provinces. After the definite establishment of American Independence, 
no peril of this kind being any longer to be feared, all navigators were 
enabled for the future to know precisely the high-road which they had 
to follow in the open sea to reach Europe most expeditiously from Amer- 
ica, and what particular line to avoid in order to effect the journey in an 
opposite direction. Toward the middle of the last century, the whalers 




fig. 23.— Koute of Steam-packets, after Maury. 



of Nantucket and the skippers of Rhode Island had already, from experi- 
ence, come to choose two difiTerent routes for going and returning. In 
order to "descend" on England, they allowed themselves to be carried 
with the Gfflf Stream, and on their return crossed this current at the 
Banks of Newfoundland, and " mounted " the Arctic counter-current ;* 
on these voyages they distanced vessels from other sea-ports on an aver- 
age by 74 miles per day. The progress of navigation permits us now to 
* J. G. Kohl, Geschichte des Golfitroms, p. 103. 



USE OF THE GULF STREAM TO SHIPS. 81 

utilize the impelling force of the cuvrents of the North Atlantic far better 
than the sailors of Providence could. The normal duration of the passage 
lias been reduced to half. Eight weeks were formerly reckoned for a 
voyage from England to the United States; now four weeks suffice for 
sailing-vessels, and some have even made the journey in seventeen days 
only. Steamers, which also have a double route too, in order to avail 
themselves of tlie current, accomplish the passage in nine or ten days. 
For commerce, civilization, and the brotherhood of peoples, such a result 
is not less important than as if the continents themselves were shifted, so 
as to reduce by three-quarters the width of the ocean which separates 
them. 

6 



82 THE OCEAN. 



CHAPTER IX. 

CUKEENTS OF THE SOUTH ATLANTIC AND THE INDIAN OCEAN. — DOUBLE 
EDDY OP THE PACIFIC OCEAN. 

The circuit of the waters which occurs to the south of the equator, in 
the southern basin of the Atlantic, is much less known than that of which 
the Gulf Stream forms a part; but all that has been observed of it by 
navigators proves that the movements of the liquid mass are analogous 
in the two hemis]3heres. A current of cold water, coming from the Ant- 
arctic seas, dashes against the Lagullas Bank to the south of the African 
continent and divides into, two branches, one of which re-enters the In- 
dian Ocean, while the other flows along the western coast of Africa, pen- 
etrates into the Gulf of Guinea, and, in consequence of the motion of the 
earth, bends toward the west in a wide semicircle. To the south of the 
Cape Verd Islands, the waters coming from the southern seas join those 
which flow from the icy sea of the north, and uniting into one river of 
500 to 1000 miles wide, move slowly in the direction of South America 
and the Antilles. The greater mass of water approaches the continent 
to the north of Cape St. Roque, the advanced promontory of Brazil, and, 
flowing to the north-west along the coasts of Guiana and Columbia, en- 
ters the Caribbean Sea, there to form the Gulf Stream, A less consid- 
erable fraction of the equatorial current bends to the south of Cape St. 
Roque, and follows the Brazilian coast-line to the south-west. But in 
descending toward latitudes nearer and nearer the southern pole, the 
warmer current from the equator incessantly gains on the rotatory move- 
ment of the earth ; consequently, it bends more to the south than to the 
south-east, and forming a sort of gulf stream in an opposite direction, it 
strikes the polar current to the east of the Falkland Isles, whose position 
in the southern hemisphere corresponds to that of ]Sre\^foundland in the 
northern hemisphere. There the warm current, after having deposited 
drift-wood, taken from tlie Brazilian coast, on the shores of the Falkland 
Islands, sinks below the lighter strata of the glacial current ; while the 
latter directs its course to the north-east toward St. Helena, where it joins 
the great equatorial river. The whole circuit is accomplished in a period 
which may be estimated at about two or three years.* 

Dissimilar, and often contradictory, observations recorded by various 
navigators who have studied the phenomena of the waters in the South 
Atlantic, seem to put it beyond doubt that the currents of this basin 
have not the same regidarity, of course, as those of the Northern Atlantic. 
It frequently happens that the water does not flow in the direction indi- 
cated on ma|)s, or even tends in an opposite direction to the normal move- 
* Mittheilungen von Petermann, t. x., 1866. 



CURRENTS OF THE SOUTH ATLANTIC. 83 

ment. The reason of this difference between the two basins is quite nat- 
ural. While the North Atlantic is a very regular sea in its general form, 
bounded on each side by almost parallel shores, the marine area lying be- 
tween Africa and South America expands very widely from the coast of 
the southern polar land. It may be considered simply as a gulf of the 
great ocean, which extends around the globe to the south of the extremi- 
ties of the three southern continents. As a consequence of this irregular 
disposition of the coasts, the variations from the normal circumstances of 
the waters can not fail to be very great. The cold waters from the Ant- 
arctic Pole, charged with fragments of ice-fields and icebergs, flow, it is 
true, Avith a continuous motion to replace the vapors which rise incessant- 
ly from the equatorial Atlantic ; but the regular play of the currents is 
modified, now at one point now at another, according to the greater or 
less activity of evaporation in those parts of the sea. Besides, the chang- 
ing coast winds, which blow alternately from the ocean to the land and 
from the land to the ocean, impress their varying movements on its sur- 
face. 

The Indian Ocean has likewise its great circuit of water. There, too, 
the mass of fluid, chilled by its sojourn in the icy zone, is incessantly 
flowing toward the equator, in order to fill up the vacancy produced by 
the annual evaporation of thirteen to sixteen feet. It flows along the 
western coast of Australia, and afterward unites with the waters that 
come from the Pacific Ocean, through Torres Straits and the East Indian 
Archipelago. But there the regular current seems to lose itself; and we 
only see in the gulfs of Bengal and Oman marine rivers changing their 
course with the monsoons. Nevertheless, it must really be that the gen- 
eral movement of the waters is continued from the east to the west 
around the vast basin ; for on the eastern coast of Africa a current of 
warm water, iflcessantly supplied by the seas which bathe Hindostan and 
Arabia, flows to the south-west, and, under the name of the Mozambique 
Current, passes between the Island of Madagascar and the continent, 
touches the edge of the great submarine bank of Lagullas, and spreads 
into the Antarctic Ocean, after having mingled a part of its waters in 
the great whirlpool of the Atlantic. At the part whereitt is narrowest, 
the Mozambique Current is almost as rapid as the Gulf Stream, and 
moves with a speed of about A^ miles an hour. In the centre of the 
eddy in the waters of the Indian Ocean, as in the North Atlantic, Avhole 
meadows of sea- weed spread over the calm waters. 

The circuit of the currents commences in the great Pacific Ocean in the 
same manner as in the other basins. An immense river of cold water of 
unknown breadth strikes the Island of Magellan, at the south of America, 
and divides into two partial currents, one of which, penetrating into the 
Atlantic to the east of the Falkland Isles, where ice never comes, joins in 
the great round of waters between Africa and Brazil, while the other 
flows directly to the north along the coasts of Patagonia, Chili, and Peru; 
this is Humboldt's Current, thus named after the celebrated traveler who 



84 THE OCEAK 

first recognized its existence. It carries with it large icebergs, often la- 
den with stones and fragments that have fallen from the Antarctic mount- 
ains, and by the coldness of its waters produces a remarkable lowering 
of the temperature in all the countries whose shores it bathes. This liq- 
uid mass, which has a depth of no less than 670 fathoms on the coast of 
Chili, gives to the vegetation of the country a remarkable analogy with 
that of St. Helena, which at a distance of 4000 miles is washed by anoth- 
er branch of the Antarctic current. Humboldt and Duperrey state, that 
off the coasts of Callao and Guayaquil — that is to say, in one of the driest 
climates and most exposed to the rays of the sun — the current is on an 
average at from 59° to 60° Fahr., while the adjacent seas are about 20° 
warmer. Not a branch of coral can take root on the rocks and shores 
washed by this current of cold water: the polar current changes every 
thing on its passage — the flora, fauna, climate, and even the history of 
mankind. If the air was not constantly refreshed by the contact of cold 
water coming from the pole, Peru, which is so rarely watered by rain, 
would be transformed into another Desert of Sahara, and human life 
would become almost impossible there. By this current, too, the dis- 
tances are notably diminished, and Valparaiso, Coquimbo, Arica, Callao, 
are, in reality, less distant from Europe than they appear on the map ; for 
after having rounded Cape Horn, the ships sailing along the western 
coasts of South America are carried about fifteen to twenty miles a day 
by this current. 

Widening more and more on the side of the open sea, Humboldt's Cur- 
rent ends by abandoning the coast-line, and, bending toward the west, to 
mix its waters with those of the equatorial current tending from east to 
west across the Pacific. This liquid moving mass is undoubtedly the 
most powerful oceanic river of our planet. According to Duperrey, it 
has a mean width of no less than 3500 miles, from the twenty-sixth de- 
gree of south latitude to the twenty-fourth degree of north latitude, and 
on its immense journey in a straight line round the world, it traverses 
from 130 to 140 degrees of longitude — that is to say, more than a third 
of the circumference of the globe. Its average speed is, like that of Hum- 
boldt's Currentfabout 19 miles per day; but in certain places, according 
to the seasons, an advance twice as rapid has been ascertained. What 
the quantity of this enormous mass of water can be that is thus displaced 
from one end of the sea to the other, is unknown ; for it would be first 
necessary to know the mean depth of the current, but this the sounding- 
lead has not yet discovered. It is only known that at the point where 
the water from the pole turns toward the west to enter the great equa- 
torial stream, it proceeds " en masse " in one direction, with a dejDth of 
not less than a mile. 

In the midst of the innumerable islands which are scattered over the Pa- 
cific, the general regularity of the great current is frequently disturbed, at 
least on the surface, in consequence of evaporation, rains, and even by the 
incessant labors of the coral-building zoophytes, which in various ways 



Tkc OroMiiX-. 



OCEANIC 




En^^bjETharcL. 



HAMPER 5<^ B; 



R R ENTS 



PL VI 




o |c: K )a ."is:// / 



Dravra "by AVuiliemin. 



5. NEW YHRK 



THE GREAT EQUATORIAL CURRENT. 85 

disturb the cquilibriura of the ocean. But undei" the thveefokl influence 
of the terrestrial rotation, the trade-winds, and the great tidal wave 
which is propagated from east to west across the ocean,* the quantity of 
water moved each day toward the west is certainly several tens of thou- 
sands of cubic miles. The only anomaly in this prodigious movement of 
the waters of the Pacific which seems inexplicable is the existence of an 
oceanic river flowing in an opposite direction to the principal current. 
This reflux has been observed to the north of the equator over a mean 
breadth of upward of 300 miles ; elsewhere its speed is variable, and its 
advance is not always in the direction of due east. In the absence of 
measurements and positive experiments which permit us to give an ex- 
act account of the progress of this counter-current in the difierent sea- 
sons, several hypotheses have been suggested to explain its origin. The 
common opinion is that it is masses of water turned aside on their course 
and thrown back by submarine plateaus.f Nevertheless, it is much sim- 
pler to admit that this is a normal phenomenon, for in the Atlantic Ocean 
it has also been established that some lateral eddies tend in an opposite 
direction from the great liquid mass flowing from east to west. 

When it has arrived at the end of its voyage across the Pacific, the 
equatorial current must of necessity change its direction. A portion of 
its waters, driven now in one direction and now in another by the mon- 
soons which succeed one another on the borders of the continents of Asia 
and Australia, flows into the Indian Ocean by the shallow straits of the 
East India Islands. But the greater mass of the current is thrown back 
either to the south or to the north, by the resistance of the shores against 
which it «lashes and breaks. The half of the current which strikes the 
coasts of Australia diverges toward the south, and flows in the direction 
of the Antarctic lands. It thus flows in the opposite direction to the po- 
lar current, which it finally encounters to the south of New Zealand, and 
plunges beneath its colder waters, which by their freshness are rendered 
lighter. To the east and north-east the current of the Antarctic seas 
completes the enormous circuit described by the waters in the southern 
basin of the Pacific. 

The other half of the equatorial current, diverted by New Guinea, the 
Philippmes, and that long barrier of islands lying to the east of China, 
bends gradually toward the north and flows along the outer coasts of 
Japan. It is the Gulf Stream of the Pacific Ocean, called also Tessan's 
Current, after the navigator who revealed its existence to the savants of 
Europe. But for centuries, and perhaps thousands of years, the Japa- 
nese have known and prized it highly for their coast-navigation. They 
give it the name of Kuro-Sivo, or " Black River," doubtless because of 
the deep blue of its waters. Less rapid than the Gulf Stream, its ad- 
vance is nevei'theless, on an average, more than 1^ miles per hour, and in 
many places very much exceeds this speed. Before Yeddo its mean tem- 
perature is '75"2° Fahr. — that is to say, about 10° to 12° Fahr. higher than 
* See p. 102. t Herschel, Physical Geography. 



86 THE OCEAN. 

the Still waters beside it. Furthermore, the Kuro-Sivo, like the Gulf 
Stream, is com]josecl of liquid bands of unequal temperature flowing be- 
side each other like two distinct rivers in the same bed. 

In passing the largest island of Japan,* the Black River, obedient to 
the impelling force which the rotation of the earth has communicated to 
it nnder troj)ical latitudes, already commences to bend toward the north- 
east, and, spreading over a vast extent, loses in depth what it gains in 
surface. To the north of Japan, it meets obliquely a current of cold wa- 
ter emerging from the Sea of Okhotsk, to replace in part the void caused 
by the evaporation in the equatorial seas. Tliick fogs, similar to those 
of the Banks of Newfoundland, rest above the spot, of contact between 
the warm and cold waters. Shoals of fish, the object of pursuit to fisher- 
men, i^eople this maritime zone, which serves as a limit between the, two 
currents, and where the mass of animalcula and remains brought from the 
trojDics is joined to those which are conveyed in the waves coming from 
the north. Still, the phenomena presented by the meeting of the two 
currents have not the same grandeur in the North Pacific as under the 
corresponding latitudes of the Atlantic. For the mass of water flowing 
from the Sea of Okhotsk is relatively less considerable, and the opening 
of Behring's Straits, 31 miles wide and 50 fathoms deep, is of too small 
dimensions to allow much water from the icy ocean to penetrate into the 
Pacific. Only small coast currents, carrying the pines and firs from the 
shores of Siberia, and rounded ice-floes from along the two coasts, cross 
from one sea to the other. In summer the current which comes from the 
north, both on the eastern and western bank of the strait, is only a super- 
ficial current. On the other hand, the slight portion of the waters of the 
Black River which passes beyond the range of the Aleutian Islands to 
enter Behring's Straits is a submarine current, at least during the sum- 
mer season. Arriving in the icy sea, still warm and strongly saline, it 
mingles with the cold and light water which descends into the Atlantic 
by Bafiin's Bay.f 

The great mass of the Kuro-Sivo traverses the Northern Pacific from 
east to west with a graceful curve, no less beautiful than that formed by 
the islands that are washed by its waters; then bends gradually to the 
south-west and south, to coast the shores of California; finally, in the 
neighborhood of the tropics, it changes its direction again, and is lost in 
the equatorial current, inclosing in its circuit a floating forest of sea-weed 
hardly less extensive than that of the Pacific. 

Contrary to Humboldt's Current, which rolls its cold watei's and drives 
before it icebergs to refresh the dry and burning atmosphere of Peru, the 
Gulf Stream of the Japanese carries along the coasts of Sitka and Van- 
couver's Island a mass of waters warmed by a long sojourn under tropical 
heat, and by its vapors brings spring to regions which without it would 
have a very severe winter. It bears on its waves the fragments which it 

* De Kerhallet, Considerations sur V Ocean Pacijique. 
t De Haven ; Miihiy ; Gustave Lambert. 



THE ''KUItO-SIVO;' Oli TESSAN'8 CURRENT. 87 

lias received from the coasts of the Moluccas, the Philippinesj and Japan. 
To the inhabitants of the Aleutian Islands and Alaska it gives, as fuel, 
camphor-wood, and other odoriferous trees from southern countries; it 
serves, too, as a highway for all kinds of waifs, carries away disabled ships, 
and numberless traditions relate how Ja^nese sailors were drifted afar 
and landed against their will on the coasts of America?. And it is per- 
liaps to au adventure of this kind that the Chinese navigators owe their 
discovery of the New World ten centuries before Columbus, if it is true 
that the country of Fusang, mentioned in the annals of China, is in fact 
the countries of Mexico and Guatemala. Messrs. Neumann, d'Eichthal, 
and other learned scholars do not doubt the authenticity of this historical 
fact. 



THE OCEAN. 



CHAPTER X. 

LATERAL EDDIES. — EENNELl's CTJEEENT. — COUNTEK-CUEEENT IN THE SEA 

OP THE ANTILLES. EQUILIBEIUM OP THE WATEES IN THE BALTIC, THE 

BOSPOEUS, AT THE ENTEANCES TO THE MEDITEEEANEAN AND THE BED 
SEAS. — EXCHANGE OP WATEE AND SALT BETWEEN THE SEAS, 

None of those great currents which wind through the oceanic basins 
show, in their exterior contours, the same sinuosities as the seas through 
which they flow. While most of the shores present a succession of prom- 
ontories and gulfs, the currents stretch in long regular curves, which in 
their vast sweep indicate but generally the form of the depression which 
contains them. Every considerable gulf which is separated from the 
ocean by any projecting land remains outside the whirlpool of waters, 
unless it should be in the very axis of the current, like the sea of the An- 
tilles. Yet even in those parts, which do not share in the general circu- 
lation, the waters do not remain perfectly stationary. They also have 
their circulatory system, and it is from the gi-eat maritime current that 
each secondary eddy receives its impulsion. 

A remarkable example of these currents of the secondary order is pre- 
sented on the west of Europe, in the semicircular basin formed by the 
coasts of Spain, France, England, and Ireland. A portion of the waters 
of the Gulf Sti'eam coming from the north and north-west strikes the 
coasts of Galicia and the Asturias ; it turns east toward the extremity 
of the Gulf of Gascony, flows along the shore of the Landes, then that of 
Saintonge, Poitou, Bretagne, and, returning in a north-west and west 
direction, forms a sort of liquid barrier across the Channel. To the south 
of Cape Clear, this oceanic river, known under the name of Rennell's Cur- 
rent, after the English savant who discovered its existence, finally enters 
the Gulf Stream, and returns to the south with the waters of the ocean. 
Thus a complete circuit, is made around the basin, analogous to that which 
occurs in each of the great oceans of the world. Rennell's Current, in 
its turn, coasting at a greater or less distance the shores of the continent, 
sends out into the little bays currents of a third order, which also com- 
plete their circular movement, like the Gulf Stream and the Kuro-Sivo ; 
and so, by lateral transmission, the circulation of the waters is continued 
from oceans to gulfs, from gulfs to bays, and from these to the creeks. 
These secondary currents, howevei", are usually much less regular than the 
general currents, and navigators have ascertained that at times Rennell's 
Current has flowed in a completely reversed way to its normal direction.* 

Secondary currents generally move in a course exactly oppQsite to that 
of the principal stream, of which they are only a branch bent back on it- 
* Gareis and Becker, Physiographie des Meeres. 



EQUILIBRIUM OF WATERS IN THE BALTIC, ETC. 89 

self. Either permanently or temporarily they are found in all seas, open . 
or inland, in all gulfs and bays of the ocean. Even the sea of the vVn- 
tilles, the waters of which are carried almost en masse toward the Gulf 
of Mexico, presents at its western extremity a permanent current, which 
tends from the shores of the isthmus to those of Colombia. A vessel 
drifted by the principal current into the neighborhood of Nicaragua 
would only have to ascend to Colon, and then abandon itself to the waves 
in order easily to accomplish its return voyage, born^ by the waters which 
flow incessantly in the direction of Carthagena ancl Santa Marta. Many 
lazy seamen never pass from the ports of the isthmus to those of terra 
firma in any other way. Regardless of time, they let themselves be 
rocked by the billows without even taking the trouble to hoist the sails. 
Their bark, slower than a tortoise, advances at the most but a mile an 
hour, and, after eight or ten days spent on the passage, they finally per- 
ceive the bluish mountains of New Granada, and its sandy shores shaded 
by cocoa-nut trees. ' 

There are some currents which are evidently produced by a disturbance 
of equilibrium between two levels. Thus the Baltic Sea, which receives 
more water by the contributions of rivers than it loses by evaporation, 
must necessarily distribute its superfluity in the North Sea through the 
straits of the Sound and the two Belts. Nevertheless, these outlets being 
large and deep enough to difi'use the superabundant water in a little 
time, the current is not permanent. Waves from the North Sea, driven 
into the Baltic by the westerly winds, frequently meet it, and from this 
conflict of waters arise local and unexjDCCted movements dangerous to 
ships. Every four days the waters on the surface flow on an average for 
forty-eight hours toward the Categat, then flow back into the Baltic for 
one day, and during another day there is no sensible movement in either 
direction. Often, too, according to Forchhammer, the two contrary cur- 
rents glide one above the other ; the lighter on the surface, coming from 
the Baltic, and the other from the North Sea, heavier by reason of the 
salt it contains, flowing beneath. 

At the other extremity of Europe similar phenomena occur in the Bos- 
porus, at the outlet of the Black Sea. This strait, which receives the 
superabundant waters of the Euxine, presents a mean breadth of more 
than a mile, with a depth of 15 fathoms ;* so that if the waters of the sea 
flowed there in a continuous manner as in the bed of a river, and the 
swiftness of the current were only about \^ miles per hour, it would not 
discharge less than nearly 36,000 cubic yards per second. But it is prob- 
able that all the united afiluents of the Black Sea and the Sea of Azof 
supply hardly the half of this quantity; and, besides, a great part of the 
water brought by them is carried ofl" again by evaporation. The Bos- 
porus is, therefore, too large to serve -as the bed of a single current flow- 
ing from the Black Sea into the Sea of 'Marmora. It has been observed 
that the waters ordinarily descend toward the Mediterranean, with a 
* Tchihatchef, Asie Mineure. 



90 



THE OCEAN. 



speed of from two to four miles an hour ; but the existence of tolerably- 
rapid lateral counter-currents has also been established; and sometimes 
the winds blowing from the west cause the principal current to flow back 
through the strait. A submarine movement of the waters in the direc- 
tion of the Black Sea also exists, as already ascertained by Marsigli in 
the last century. 

At the western part of the Mediterranean, between Gibraltar and Ceu- 
ta, the normal current is that coming from the ocean. In fact, the Med- 
iterranean has not many considerable tributaries. It only receives a sin- 
gle river having a really great mass of water, namely, the Danube ; its 
other affluents of any importance — the Rhone, the Po, the Dniester, the 
Dnieper, the Don, and the Nile — bring, on an average, not more than 19,620 
cubic yards of water per second.* On the other hand, evaporation is very 




^ A'S-J T//c^ .rondj'nt/s are 



Pig. '24.— The Straits of Gibraltar. 

rapid in the basin of the Mediterranean, especially on the coasts of Egypt 
and Tripoli. We may admit that the quantity of water taken from this 
basin by the solar rays, and not directly restored bj'- rain, annually repre- 
sents a section of about 4|- feet; which is probably near enough to the 

* See the section entitled Rivers. 



CURRENTS OF THE RED SEA. 



91 



trutli, as in the neighborhood of Genoa, Beaucaire, Aries, and Perpignan, 
on tl)e northern shores of tlie sea, tlie evaporation exceeds four-tentlis of 
an inch per day in the great heat, and nearly two feet during the three 
summer months,* while the amount of rain during the year is about 1 9^ 
inches. The result is that the Mediterranean constantly loses three times 
as much water as it receives by its tributaries. It is the ocean, then, 
Avhich must fill up the void ; a portion of the current which flows from 
north to south along the coasts of Portugal and Spain enters by the 
Straits of Gibraltar, and spreads far into the Mediterranean in superficial 
sheets. Nevertheless, if this inland sea did not also send a counter-cur- 
rent to the Atlantic^ it w^ould sooner or later be changed into an immense 
plain of salt. Incessantly losing fresh water by evaporation, and always 
receiving salt water from the ocean, its liquid mass would become in the 
end completely saturated, and the crystals of salt would line the marine 
bed in ever-increasing layers. In order that the equilibrium of saltness 
between the two seas should not be interrupted, it is necessary that the 
Mediterranean should send its saltest waters to the Atlantic. This is, in 
fact, what takes place. Besides the lateral eddies that occur along the 
shores an each side of the current coming from the Atlantic, a Mediter- 
ranean counter-current flows below the lighter superficial waters, and 




Fig. 25..— Profile of the Straits of Gibraltar. 

takes its direction toward the ocean. This submarine river, which passes 
the Straits of Gibraltar to be lost in the open sea, is, as chemical analyses 
have shown, a current of heavy water almost saturated with salt. Thus 
an exchange is accomplished through that nari-ow passage ; the Atlantic 
gives to the Mediterranean the waters wdiich it needs, and receives in re- 
turn its superfluity of salt to diff'use through the ocean. The sea endeav- 
ors incessantly to re-establish its constantly disturbed equality at the 
boundary of the two marine basins, at a depth of about 546 fatlioms. 

This harmony of the forces of nature is shown in a still more striking 
manner at the entrance to the Red Sea. This elongated gulf, which is 
nearly 1480 miles in length from the Straits of Babel-Mandeb to Suez, re- 
ceives from the atmosphere and the bordering countries so slight a quan- 
tity of Avater that it may be considered as absolutely nothing. It rains 
but very rarely (jver the sheet of water lying between the two deserts of 
Egypt and Arabia, and not a single torrent brings down its waters to it. 
* Regy, Annates des Fonts et Chaussees, 18G3. Vigan, ibid., 186G. 



92 THE OCEAN. 

The Red Sea is therefore only an immense basin of evaporation, and the 
annual loss is all the greater that the rays of the sun shine almost always 
from a cloudless sky. The portion of fluid transformed into vapor is es- 
timated at about eight-tenths of an inch per 24 hours — that is to say, 
nearly 23 feet per year; so that if the gulf was completely closed, the wa- 
ter, whose mean depth does not exceed 220 fathoms, would be entirely 
dried up in the space of sixty years. Owing to their higher level, the 
waves of the Indian Ocean are carried into the Arabian Gulf by the Straits 
of Babel-Mandeb ; and this flow, superficial or submarine, must make itself 
felt with all the more force, because during eight ^months of the year the 
winds blow from the north to the south precisely in the axis of the Red 
Sea, and would thus tend to empty the gulf, if the Taws of gravity per 
mitted. But whatever be the swiftness of the current coming from the 
Indian Ocean, a portion of its water evaporates on the way, and, in con- 
sequence, the liquid mass, diminished by a certain quantity from evapo- 
ration,, must become Salter and salter in proportion as it advances to the 
north. In fact, it has been established by direct analyses that the quan- 
tity of salt contained in the same volume of water increases gradually 
from Aden to Suez. From a little more than 39 parts in a thousand at 
the entrance to the gulf, it rises to 41 and even 43 parts in the thousand 
at the northern extremity.* Dr. Buist, a scholar of Bombay, has cal- 
culated that if the Red Sea did not return to the ocean the salt that is 
concentrated there in consequence of evaporation, it would end in being 
changed into a solid mass of salt in a space of time certainly less than 
three thousand years, and perhaps in only fifteen or twenty centuries»f 
Now the Red Sea has already existed for thousands and thousands of 
years, and its waters (more salt than those of other seas, it is true) are 
still very far from being in a state of saturation. We therefore come 
to this inevitable conclusion, that a very salt submarine current flows 
through the Straits of Babel-Mandeb into the Indian Ocean in an oppo- 
site direction, and below^ the superficial current which supplies the Ara- 
bian Gulf As in houses each door serves at the same time as a passage 
for two contrary currents — that of the warmer and lighter air which es- 
capes above, and that of the colder and heavier air penetrating below — so 
in the seas each strait is traversed by two streams diiferent in tempera- 
ture and in their saline contents. 

All these phenomena of exchange, which occur in such a striking man- 
ner at th^ entrance to the Red Sea, the Mediterranean, and the Baltic, 
are reproduced in the vast space of the seas wherever the equilibrium of 
level, warmth, or saltness is disturbed by any cause whatever. Thus 
the Atlantic, much better supplied than the South Sea as regards rains 
and aflluents, is nevertheless not more elevated; and on its side the Pa- 
cific does not contain a greater quantity of salt than the other oceans. 
On all parts of the planet, seas bathing the shores of countries most di- 
verse in appeai'ance and geological formation have a tendency to resem- 
* See p. 36. t Mauiy, Geography of the Sea. 



INTERCHANGE OF WATER AND SALT. 



93 



ble each other iu their composition, saltuess, and in most of the other 
phenomena of tlieir waters. The currents are the great agents in pro- 
ducing this equilibrium in the seas ; but by their very mobility, their de- 
pendence on the seasons, winds, configuration of the coasts, and, finally, 
by reason of the submarine part of their course, they are exceedingly 
difficult to observe in a systematic manner; and among the numerous 
general and partial currents, there is not a single one, not even the Gulf 
Stream, whose normal course can be traced with complete precision. 
Happily, scientific observations are now being multiplied over all the 
seas; they add to and unite with one another; and, little by little, ap- 
proach the truth by approximations which result from the comparison of 
facts. Every new sounding, every new thermometrical reading, is an ac- 
quisition to science, and allows us to follow with a clearer eye the com- 
plicated circulation of the waters in the immeu'se labyrinth of the ocean. 



94 THE OCEAN. 



BOOK III— THE TIDES. 



CHAPTER XI. 

OSCILLATIONS OP THE LEVEL OP THE SEAS. — THEORY OP THE TIDES. 

Another movement which keeps the waters of the sea in a constant 
agitation is that of the tides. While the currents cany the waves from 
one pole to the other, and -stir the very mass of the ocean, the tides inces- 
santly modify the level by the alternations of ebb and flow^ which they 
impart to its waters. They raise or depress without relaxation the mass 
of waves on all the shores of the globe ; the strand, which by turns they 
invade and lay bare, becomes debatable ground between the two elements, 
and successively forms a part of the oceanic basin and the continental 
surface. Twice a day vast plains of sand- like those of Mount St. Michael 
are invaded by the waves, deej) bays are formed far into the land, and 
barks glide with sails spread above the path which the pedestrian has 
just quitted. Twice a day the same tidal wave causes the waters brought 
to it from the continents to return back again, transforms simj)le rivulets 
into large rivers, changes basins filled with mud into vast inland harbors, 
and carries fleets of ships over sand-banks and hidden rocks. Six hours 
afterward all is changed. The tidal ports are strewn with ships stranded 
and lying in the mud, the mouths of rivers allow their islands of alluvium 
to emerge, and great bays are no more than plains of sand. Thus the 
outline of continents incessantly changes in appearance; the girdle of 
estuaries and ports, beaches, rocks, and sand-banks, which surrounds their 
coasts, continually alters, and changes the geography of the shores in 
the same proportion. Besides, movements so considerable can not occur 
without being accompanied by very powerful currents, flowing alternate- 
ly from the open sea toward the coast, and from the coast to the open 
sea, and contributing greatly to the general circulation and mingling of 
the waters in the ocean. The influence which the ebb and flow of the 
tides exercises indirectly on the commerce and civilization of nations is 
immense ; it is to these movements of the sea that England owes in great 
part her power and glory. 

In all times the people dwelling on the borders of the ocean have un- 
derstood, without being able to account for.it, that the alternate j^henom- 
ena of ebb and flow depend on the position of the moon and sun relatively 
to the earth. The coincidences that they saw renewed each day between 
the movements of the tides and those of the large heavenly bodies could 
not leave them in any doubt of this. Sailors and fishermen, accustomed 



THEORY OF THE TIDES. 95 

to look to the sky for the signs of the weather, and indications of the 
route which they ought to follow, had no trouble in ascertaining that the 
return of every second tide corresponds exactly to the passage of the 
moon over the same degree of the heavens — that is to say, to the com- 
mencement of a new lunar day. Following the phases of the moon — at 
new, half-moon, or full — they saw the tides •change in a regular manner, 
and become successively higher and higher, and afterward, from day to 
day, lower, till the end of the lunar month. Finally, the movements of 
the sun also announced to them beforehand the approaching state of the 
waves, for the equinoxes of March and September are always accom- 
panied by very high tides. These coincidences between the jihenomena 
of the sea and the movements of the moon and sun are so striking, that 
all barbarous maritime tribes have remarked them, and have rudely sym- 
bolized the idea in their songs. Thus the Scandinavian sagas represent 
Thor, the god of winds, blowing the water with a horn which he plunges 
into the depths of the ocean, and by his powerful breath causing the 
waves to rise and fall by turns. What can this strange legend signify, 
if not that the regular oscillations of the tide depend oft the cosmical 
forces to which the planet itself is subject? 

Nevertheless, these symbolic tales of the ancient Scandinavians are far 
removed from that scientific theory of the tides which the researches and 
sagacity of Newton and Laplace have established. Even Pliny, when he 
affirmed clearly that the tides are due "to the combined influences of the 
sun and moon," restricted himself to summing up in precise terms what 
all the dwellers on the shores of the ocean knew ; but he could not ex- 
plain in what manner this influence was exercised. The explanation of 
the mysterious phenomena of the periodical swelling of the waters could 
only be attempted, in modern times, with the aid of the knowledge ob-^ 
tained by astronomers on the motion of the celestial bodies, and with the 
powerful means of investigation which mathematicians have supplied 
them with. Kepler first indicated the course to be followed; and Des- 
cartes, and then Newton, each gave his theory explaining the tides — the 
one by pressure, the other by the attraction exercised by the sun and 
moon on the mobile waters of the sea. It is the latter theory, that of 
Newton, which was developed later, much modified by Bernouilli, Euler, 
and Laplace, and which Lubbock, Whewell, Chazallon, and so many oth- 
er natural philosophers have since compared with observations made on 
the. shores of the ocean. Being very satisfactory in most respects, it is 
now very generally accepted : but it still has eminent opponents, among 
whom F. Bouchei^orn* must be named ; many of the secondary facts are 
still to be elucidated, and many local phenomena are not yet understood. 
To follow the tides in their progress and fluctuations across the seas, it is 
not sufficient to know the law^ of gravitation, and to calculate with the 
most I'igorous exactitude the movement and position of the heavenly 
bodies; one must also know all the facts relative to the movements of 
• * Philosophic Naturelle, pp. 1-205. 



96 ■ THE OCEAN. 

fluids, and know liow to apply to all their phenomena of acceleration, 
retardation, increase, interference, and equilibrium the most complicated 
and most minute formulae of high mathematics. It would also be indis- 
pensable to know eyery fact respecting the form of the shore, and the 
inequalities of the bed of the sea. 

Reduced to its principal 'elements, the theory of tides set forth by 
Laplace, and generally adopted since, is very simple. The earth is not 
an isolated body in sj)ace; it is attracted by all the nearer heavenly 
bodies, and it is, indeed, in great part this force of gravitation which 
causes it to turn round the sun, and retains the moon as its satellite. Let 
us imagine for an instant the earth to be covered with water over all its 
surface, and subject to the attraction of the moon alone. This sujjerficial 
part of the planet would be more strongly attracted than the solid por- 
tion, since it is nearer to the moon which attracts it; and owing to the 
facility with which liquid particles glide one over the other, it would 
swell, so to say, toward the moon till its weight would be in equilibrium 
with the attracting force. It would then form an intumescence, the sum- 
mit of which would be exactly on the ideal line which unites the centre 
of the earth to that of the moon. On the other side of the planet, accord- 
ing to the general theory, the w^aters ought to swell in a corresponding 
wave, and that from a precisely contrary cause. The liquid strata on this 
part of the earth being farther from the moon than the solid kernel, are 
less atti'acted than it, and in consequence must remain slightly behind, 




Fisr. 26.*— Lunar Tide. 



thus forming a new intumescence, the summit of which will be found on 
a prolongation of the line uniting the planet with its satellite. Considered 
as a whole, the mass of marine waters woifld thus assume the form of an 
ellipsoid, having its greater axis directed toward the moon, which is the 
* This illustration, as well as Tigs. 27 and 29, have been borrowed from the fine work by 
M. Ame'dee Gnillemin, entitled Le del. 



THEORY OF THE TIDES. 



97 



i-entrc of attraction. It results from tliis, that the tide ought to be noth- 
ing at all, or very slight, at the poles; since, in its revolution, the moon, 
wliile moving to the north and south of the equator, maintains itself at 
the zenith of tropical or sub-tropical regions. 

If the earth remained immovable, these two waves would advance 
slowly, following the course of the moon ; but in consequence of the ro- 




Fig. 27. — Syzygy Tide, during the New Moon. # 

tation of the earth, they ought to move rapidly in pursuit of one another 
over its circumference — the wave of the greatest attraction moving in- 
cessantly over the part lighted by the rays of tlie moon, while the wave 
of the weakest attraction is propagated from the other side of the eartli 
on the part farthest from the satellite. In the space of a lunar day — that 



98 



THE OCEAN. 



is to say, within the 24 hours 50 minutes during which the earth has suc- 
cessively presented all parts of its surface to the planet which accompa- 
nies it — the two waves ought each to accorajjlish a complete circuit around 
the globe, and each should have a total duration of 12 hours 25 minutes. 
This is, in fact, what takes place over all seas. As to the numerous vari- 
ations presented by this phenomenon, in its height and the precise mo- 




Fig. 28.— S\ 7ygy Tide, dariug Full Moon. 

ment of its appearance, they depend on the obstacles of every kind which 
the rocks, islands, continents, oceanic currents, and winds oppose to the 
free circulation of the waters. 

Nevertheless, the moon is not the only heavenly body whose attraction 
is manifested in a sensible manner on the waves of the ocean. The sun, 
which draws the moon in its immense orbit across the heavens, is near 
enough to our planet to raise the liquid particles of our ocean also. The 



DIFFERENCE OF ATTEACTION. 



99 



total attraction exercised by the sun on the earth is even 162 times great- 
er than the total attraction of the moon ; and in consequence it would raise 
the tides into real mountains as high as the Cevennes,* if the true cause 
of the tides was not to be found in the difference of attraction exercised 
on tlie waters of the different parts of the earth. The distance from the 
moon being equal to 60 terrestrial radii only, the action of the satellite is 
much stronger over the nearer oceanic regions than over the waters situ- 
ated thousands of miles farther off. The sun, on the contrary, acts near- 
ly in the same manner on the watery particles of the whole surface of 
all the seas. According to the results obtained by the calculations of 
mathematicians, the attractive force exercised by the sun in elevating the 
waves is, as compared to that of the moon, in the proportion of about a 
third. 




JmiiiL;- l^)iiiicir;Uiire. 



Two tidal weaves, the lunar wave and the solar wave, are thus raised on 
the surface of the sea. They ought to revolve, the one in the space of 24 
hours 50 minutes, and the other in 24 hours. But these two waves, so 
distinct in their origin, are not separated in their course around the globe ; 
owing to the incessant mobility of the waters, they mix and are confused, 
and it is by calculation alone that we can discriminate in their common 
mass the part that is to be referred to each of the two heavenly bodies. 
These two united intumescences moVe together around the earth in a di- 

* 5000 to 6000 feet high. 



100 



THE OCEAN. 



vection from east to west — that is to say, in the opposite direction to the 
rotation of the globe. Serving thus as a drag upon the planet, they must, 
in the long run, lead to that slackening of its speed which the calcula- 
tions and deductions of Meyer, Tyndall, Joule, Adams, and Delaunay lead 
us to consider as inevitable.* 

When the moon, called new, turns it dark face toward us, and is thus in 
nearly the same direction as the sun relatively to the earth, the attrac- 
tions of the two great celestial bodies join together, and the two tidal 
waves, i-aised at the same time toward the same point of space, are ex- 
actly superposed. They form those tides of syzygy, or high water, called 
spring-tides, which rise to such great heights along our shores. At the 
time of full moon — that is to say, when the satellite, entirely lighted, is in 
direct opposition to the sun — new tides of syzygy not less elevated than 
the first are formed ; for, under the influence of the heavenly bodies situ- 
ated opposite to each other, a double intumescence is simultaneously pro- 
duced on both sides of the earth. During none of the other phases of 
the moon does this coincidence exist ; at the time of quadrature, the two 
great movements of the waves oppose one another, and the tidal wave, 
which represents then the lunar wave diminished by the entire solar 
wave, is less elevated than during the other phases of the moon. If the 
two attracting forces were equal in power, the neutralization of the tide 
would be complete, and the level of the sea would remain undisturbed. 

To give an idea of the fluctuations which occur during the course of an 
entire tide under the influence of the heavenly bodies, and which are va- 
riously modified by the atmospheric currents, the form of the coast, and 
inequalities of the bed of the sea, we borrow the following figure from 
Beardmore. 






TI 



Ti Til vm 



5y?3 



■■*/-^ 



3-f? 



..2j«-= 



...J4 



^ii Tm n X XI Mdi 1 tt la IV T 

Fig. 30.— Tide at Southampton, 2d August, 1859. 

The periods of the tides are exactly those of the bodies which raise 
them. The semi-diurnal period of 12 hours 25 minutes is comprised be- 
tween the passage of the moon over the two opposite meridians of the 

* See the section entitled The Earth in Space. 



FLUCTUATIONS OF THE TIDES. 101 

earth. The diurnal period, dnring which the ocean swells and subsides 
twice, corresponds exactly to the duration of one apparent rotation of the 
satellite around our planet. There is the same coincidence for the serai- 
monthly period ; the return of the spring-tides occurs from fortnight to 
fortnight with the return of the full or new moon, and the monthly period 
is completed when the series of lunar phases recommences. Nor is this 
all ; the tides have also their semi-annual period, from the equinox of 
March to that of September ; for the sun, being then directly above the 
terrestrial equator, exercises a stronger attraction on the liquid masses, 
and the Avaves of the spring-tides rise to a greater height than usual. 
Finally, an annual period is marked for the tides by the epoch when the 
earth is nearest the sun. This epoch falls during the winter of the north- 
ern hemisphere, and it is then, indeed, that the spring-tides rise with most 
force on the coasts of our continents. 

Thus the phenomena of the tides are intimately connected with the ce- 
lestial movements, and every change in the relative position of the bodies 
which attract our planet^ manifests itself by a corresponding change in 
the level of the seas. Knowing beforehand the route which the earth 
follows in space, astronomers foresee thereby even the future oscillations 
of the Avave, and can trace their curve for centuries to come. Never- 
theless, it must be admitted, this curve is only true in theory ; for if the 
tides in their origin be due to astronomical causes, they are also subject 
to variations from terrestrial phenomena. Like the winds, currents, and 
all the other manifestations of planetary life, they present incessant vari- 
ations, and are, so to say, in a continual genesis. 



102 THE OCEAN. 



CHAPTER XII. 

THEORY OP WHEWELL ON THE ORIGIN AND PROPAGATION OP TIDAL WAVES. 

— ORIGIN OP THE TIDE IN EACH OCEANIC BASIN. "ESTABLISHMENT" OF 

PORTS.—" CO-TIDAL " LINES. 

The English natural philosopher, Whewell, who during long years 
made laborious researches on the phenomena of ebb and flow, was the 
first to apply the name of "cradle of the tides" to the great continuous 
sheet of water which covers almost all the surface of the southern hemi- 
sphere. It is in this vast basin, of which all the other oceans are mere 
ramifications, that the combined attraction of the sun and moon would 
first raise that wave which from shore to shor-e dashes at length against 
the coasts of Greenland and Scandinavia. It is there that the water, a 
few instants after the passage of the moo-n over the meridian, would it- 
self attain the level of its highest •elevation, and would form that first 
regulating intumescence which the surface of all the seas would obey 
one after the other, as a coi'd shaken at one of its extremities oscillates 
to the other end in rhythmical vibrations. 

According to this theory, the tidal wave circulates incessantly through- 
out the Antarctic Ocean, to the south of the extremities of the three con- 
tinents of Australia, Africa, and South America. It follows from east to 
west the apparent course of the moon, and thus describes a real orbit 
round the" earth similar to that of the celestial bodies. Even in the Cen- 
tral Pacific and the Indian Ocean, the tide obeys this normal impulse to- 
ward the west. It strikes the coasts of Australia and New Guinea almost 
simultaneously ; then, thirteen or fourteen hours afterward, it dashes on 
the eastern coast of Africa, from the Bank of Lagullas to Cape Guarda- 
fui; finally, seven or eight hours later, the coast of South America is 
struck, in its turn, from Terra del Faego to the estuary of La Plata. 

To the north of those large oceanic tracts of the South Sea, the tides, 
not having the same facilities for developing themselves in a normal man- 
ner, would be obliged to change their direction. But, in spite of this de- 
viation, they would not the less be, Whewell thinks, continuations -of the 
primitive swelling. Arrested by the American continent, which bars its 
passage, the tidal wave would rebound toward the north, and follow the 
contoui's of the oceanic valley, like a torrent inclosed in a mountain gorge. 
Striking the coasts of America and those of the Old World, under the 
same latitude, at the same time, and at an equally oblique angle, it reaches 
almost simultaileously, on either side of the Atlantic, the Bay of Fundy 
and the Irish Channel, where its highest known elevation is observed. 
The tidal wave accomplishes this passage of about 6000 miles, from the 
Cape of Good Hope to the British Isles, in about fifteen hours. But its 



VARIATION OF THE TIDES. 103 

entire voyage, from the centre of the Antarctic Ocean, must have lasted 
' more thau a day ; and, in consequence of the gradual slackening of speed 
of the waters on the shores of Great Britain, it is only after two days and 
a half that the tidal wave reaches the mouth of the Thames. Thus the 
moon would have had time to raise five successive tides in the Pacific 
Ocean before the motion of the liquid mass would have been propagated 
to the en^-ance of the North Sea. 

Such is the theory which the labors of Whewell have caused to be long 
considered as the very expression of truth. Nevertheless, it is not cer- 
tain that things occur in this way In fact, it is ascertained that in each 
oceanic basin the tide seems to start from the centre, and to be propagated 
in all directions parallel to the general direction of the coasts. We may 
naturally conclude from this that each great division of the ocean, con- 
sidered as an isolated sea, is really the cradle of the tides which break 
upon the surrounding shores. What confirms this idea, too, which ap- 
pears so probable at first, is that the various oceans are separated from 
one another by spaces where the regular tide is hardly perceptible. Thus 
between the South and North Atlantic, whose precise boundary may be 
defined by the promontory of St. Roque and Cape Verd, there exists a 
wide zone where the tide hardly changes the maritime level more than 
about 23 to 27 inches, as at the islands of Ascension and St. Helena. Be- 
sides, according to the theory of Whewell, the tidal wave on the coasts 
of the Argentine Republic and Brazil ought to propagate itself from 
south to north ; while, on the contrary, the movement proceeds from north 
to south, from Pernambuco to the mouth of the La Plata.* When we see 
a tidal wave rise oiF the Banks of Newfoundland, in the deepest part of 
the Northern Atlantic, it is not therefore necessary to consider this as 
the same wave which twelve hours before was raised near the Bank of 
LaguUas, at the entrance to the South Atlantic, It is, perhaps, better to 
regard the oscillations which occur at the same time in both hemispheres 
as coincident but independent phenomena. 

Nevertheless, in each isolated basin the movements of the sea are much 
as Whewell has described them. On the coasts of France and the Brit- 
ish Isles the tide certainly comes from the open sea, and in its progress 
along the shores, the original motion which the attraction of the sun and 
moon produced in the middle of the open sea continually decreases. On 
penetrating into the shallower seas which surround Ireland and Great 
Britain, the tidal wave gradually slackens. After having struck Cape 
Clear and the promontory of Land's End, it is propagated with such slow- 
ness around the two islands, that nineteen hours elapse before it arrives 
at the Straits of Dover, where it meets with another livave newer by 
twelve hours, which has come by the shorlier route of the Channel. 
Whence comes this slackening of the wave? The researches of astron- 
omers and natural philosophers inform ns that the speed of the tidal 
wave is proportioned to the depths of the ocean ; driven by an equal 
* Fitzioy, Adventure and BeagJe. Appendix to vol. ii. 



104 THE OCEAN. 

force, the circumference of a wheel turns the faster the greater its diame- 
ter ; in the same way the tide hastens or slackens its movement, accord- 
ing to the depth of the watery mass which it traverses. In those lati- 
tudes where the bed. of the ocean is 5000 fathoms from the surface, the 
speed of the wave is about 528 miles an hour; where the depth is only 
about 50 fathoms, the tide is not propagated more than about 60 miles in 
the same space of time; finally, when the bottom is at about fi\^ fathoms 
below the marine surface, the movement of the waters is greatly retard- 
ed, and does not exceed fifteen miles per hour — that is to say, 440 yards 
per minute. 

In consequence of the delay which the tidal wave experiences, the " es- 
tablishment " — that is to say, the time which elapses between the passage 
of the moon over the meridian and the moment of full tide — varies sin- 
gularly in difierent ports situated near each other. Thus, while at Gib- 
raltar there is usually a coincidence between the astronomical and marine 
phenomena, and the establishment is reduced in consequence to zero, this 
interval is about an hour and fifteen minutes in the port of Cadiz, and 
four hours at Lisbon. At Bayonne, as at Lorient, it is three hours thirty 
minutes; at the mouth of the Gironde and at Cherbourg, it is seven hours 
forty minutes; at Havre, nine hours fifteen minutes; at Dieppe, ten hours 
forty minutes ; at Dunkirk, eleven hours forty-five minutes. The estab- 
lishment varies on every shore, according to the speed of propagation of 
the tide across the open seas and in the gulfs and estuaries. 

The sinuous line which unites all the points in the ocean where the full 
tide occurs exactly at the same hour, has received from Whewell the 
name oi co-tidal line; it indicates the curve which the crest of the tidal 
wave forms at any one moment on the surface of the sea. It is around 
the British Isles that these lines of simultaneous swelling or of equal 
establishment have been most carefully traced. By calculation and di- 
rect observation, that part of the oscillation on the mobile and almost 
always agitated surface of the sea, which is to be referred to the phenom- 
ena of ebb and flow, has been detected ; and much more exact maps of 
these swellings and depressions, which are invisible on the open sea, have 
been drawn, than of the vast continental regions which ai'e at present 
but little known. Thanks to the labors of Whewell, Airy, Lubbock, and 
Beechey, one can,now follow the whole series of co-tidal lines which suc- 
ceed one another from hour to hour around these two great islands, from 
the crest coming in from the open sea, at the entrance of the English 
Channel and the Irish Sea, four hours after the passage of the moon over 
the meridian, to the swelling, which nineteen hours later reaches to the 
south of the Ge*man Ocean and penetrates into the funnel of the Straits 
of Dover, where it meets the other tidal wave coming directly by the 
Channel. The general form of these curves demonstrates in a striking 
manner that the speed of propagation of the tide is in proportion to the 
depth of the seas. Everywhere we see the co-tidal lines develop their 
convex part above the deeper valleys of the marine bed; everywhere 



PROGRESS OF TIDAL WAVES. 



105 




Fig. 31.— Co-tidal Lines of the British Isles. 

w6 see the wave slacken its speed in the neighborhood of shallow rocks 
and shores. One could even, by an inspection of these lines of equal in- 
tumescence, indicate exactly those parts where the lead would descend 
lowest, so intimate is the connection of cause and effect between the 
depth of the sea and the progress of the tide. 



106 THE ocean: 



CHAPTER XIII. 

APPAEENT IREEGULAEITIES OF THE TIDES. — EXTEAOEDINAEY SIZE OF THE 

TIDAL WAVE IN CEETAIJST BAYS. INTEEFEEENCE OF EBB AND FLOW, 

DIUENAL TIDES. INEQUALITIES OF SUCCESSIVE TIDES. 

Innumeeable are the apparent inequalities which occur in the phe- 
nomena of the tides, in consequence of the inequalities of the submarine 
surface, the thousand indentations of the shore, and the alternations of 
winds and currents. Though the cause of the movement be the same 
everywhere, we can still say that at no point of the sea do the ebb and 
flow present a perfect agreement in their progress. Each promontory, 
each islet, each rock is bathed by waters having a distinct rule in the 



J 



h 



I / 
i J 

[ ( 



*}i« 



Figs. 32-34.— Irregularities in the Curves of tlie Tidal Waves resulting from the Form of the Sea-bed, 
projecting Eocks, etc. (after Lubbock). 

propagation of their tides ; every obstacle which breaks the regular course 
of the oscillations modifies the whole of the graceful curves which bend 
around it. The above figures, borrowed from Lubbock, give an idea of 
these variations in the march of the waves. 

The diflTerence which most strikes the minds of navigators and inhab- 
itants of the coast is that of the height of the tides. In one part of the 
coast the tide hardly makes itself felt, even during the equinoctial syz- 
ygies; while elsewhere every tide is a real deluge, spreading as far as 
the eye can see over vast tracts, which emerge again at the time of ebb. 
This astonishing contrast in the amplitude of the tides results from differ- 
ences of speed in the progress of the oscillations in the seas and bays of 
the coast-line. In fact, the great swelling caused by the heavenly bodies 
may be considered as formed of a great number of successive waves oc- 
cupying a considerable breadth on the surface of the sea. In the open 
ocean all these waves move with great speed ; but in proportion as they 
approach the shores they slacken their movement, and consequently must 
gain in height what they lose in rapidity. From the mere sight of a tidal 
chart we can affirm that the tide will rise several feet hisfh in all the a'ulfs 



SIZE OF THE TIDAL. WAVE. 



107 



Avhero we see the co-tidal lines crowded together, in consequence of the 
ivradual retardation of the wave of intumescence. 

In this respect, facts fully confii-ni theory. The gulfs of Bengal and 
Oman, the Chinese Sea, the indentations of the eastern coast of Patagonia, 
the Bay of Panama, that of Fundy, between New Brunswick and Nova 
Scotia, the Channel and the Irish Sea, are parts where the waves of equal 
intumescence follow each other very closely, and it is there too that a 
greater extent of coast is alternately covered and revealed by the tide. 
In the port of Panama the tides rise nearly twenty-three feet, concealing 
and discovering by turns an immense strand in their diurnal movements, 
while at hardly thirty-seven miles distant on the other coast of the isthmus 
the ebb and flow are scarcely perceptible. 

In the Persian Gulf and the Chinese Sea the amplitude of the equinoc- 
tial tide is nearly thirty-six feet at the extrejnity of the gulfs. In the 
mouth of the Severn and the French bay of Mount St. Michael the dif- ■ 
ference of height between the spring-tides and low-water is from forty- 
five to forty-eight feet. To the south of the American Continent, in the 
gulfs of San Jorge and Santa Cruz, at the entrance of the Straits of Magel- 
lan, Fitzroy has measured tides of from forty-eight to nearly sixty-six feet 




Fig. 35.— Bay of Fuudy. 



high; finally, in the Bay of Fundy, so well calculated, by the contour of 
its coasts and the surface of its bed, to retard progressively the march of 
the tide, tl^e difference between high an(f low water, which is about nine 
feet at the entrance, gradually increases to nearly sixty-nine feet toward 



108 



THE OCEAN. 



the extremity of the channel. This is probably the part of the coast 
M^here the regular oscillations of the waters are accomplished in the 
grandest manner. Twice a day immense neutral shores, which are neither 
land nor sea, change into deep gulfs, and stranded ships rise and float 
with sails spread, while towns lost in the interior of the land find them- 
selves seated on peninsulas invested by the sea. At St. John's, New 
Brunswick, a cascade is seen to glisten at the bottom of the port at low 
water; but when the tide reaches the foot of the cliff", the height of 
the fall gradually diminishes, and it is at last entirely drowned in the salt 
waters, which, spreading far over the upper terrace, permit vessels to pen- 
etrate into the natural basin formed above the cascade. 




Fig. 36— Mouth of the Avon (after Beardmore). 

Similar phenomena occur in the two bays of Mount St. Michael and 
the Severn. There, too, I'ivers and rivulets are periodically changed into 
gulfs ; there, too, the harbors are tidal ports, where ships, with the ex- 
ception of those which ai'e inclosed within the basins, lie on their sides in 
sand or mud at the time of low water. In the same way the space ex- 
tending between Noirmoutiers and the coast of La Vendee is alternately 
an isthmus and a strait ; a high-road traversed by vehicles winds through 
the sandy plain between pools of Avater, and a few hours afterward ves- 
sels with sails spread pass over the same route. Sailors are often seen 
walking quietly on the shore at a slight distance from their stranded ves- 
sel, or else digging in the ground in search of shells; but let the distant 
rolling of the tide be heard, and in the space of a few seconds the crew 
is on board, prej)arations are made for a new embarkation, and the vessel, 
raised by the tide, sails rapidly over the sea. 

It is in the Bay of St. Michael, on the western coast of Europe, that the 
rising tide presents the grandest spectacle, for in the centre of the bay 
rises a black granitic rock — "abbey, cloistez', fortress, and prison" at the 
same time — which by its abrupt precipices and its " titanic pile, rock upon 
rock, century after century, but always dungeon over dungeon," contrasts 
Avith the dreary extent of the shore.* At low water, the immense sandy 
plain, above 150 square miles in extent, resembles a bed of ashes. But 
when the tide, swifter than a h(fi'se at full gallop, rises foaming over the 
* Michelet, La Mer, p. 18. 



riie Oci'au Ac 



BAY OF S"^ MICHEL 



PI VII. 



' )Y '4- 




Drauwn by AAnjilleiuiii 



38000C 
t s ■* 6 e 1 a 



Erii^ra-ved byl^rhard 



TIDES IiV THE BA Y OF ST. MICHAEL. 



109 



scarcely perceptible slope, a few hours are sufficient to transform the 
whole bay into a sheet of g'rayish water, penetrating far up the nioutlis 
of the rivers as far as the quays of Avranches and Pontorson. At the ebb, 
the waters retire with the same speed to nearly six and a quarter miles 
from the shore, and lay bare the great desert strand, which is intersected 




Dcjjtli andieated m feet 
Fig. 37.— Straits of Noirmoutiers. 



by the subterranean deltas of tributary rivulets, forming here and there 
treacherous abysses of soft mud, into which travelers are in danger of 
sinking. At the time of spring-tides the liquid mass which penetrates 
into the bay is estimated at more than 1470 millions of cubic yards, and 
even at neap-tides the deluge, which pours over the beach twice in the 



110 



THE OCEAN. 



four-and-twenty hours, is not less than about 765 millions of cubic yards.* 
Is it astonishing that such torrents should have been able in former times, 
when driven by tempests, to break through the chain of sand-hills which 
protected the rocks of Tombelene and St. Michael on the north, and to 
transform into sterile wastes the beautiful country and vast forests which 
extended to the foot of the peninsula of Cotentin ?f 

Beechey's observations of the tides of the Channel and the Irish Sea 
cause it to be regarded as certain that the enormous amplitude of the ebb 
and flow at the mouth of the Severn, and in the bays of Cancale and St. 
Malo, arises, not only from the gradual elevation of the bottom, but also 
from the sujjerposition of two waves, which encounter each other. In 
fact, the crest of the tide which penetrates into the Irish Channel meets, 
at the end of the gulf where the'Severn discharges itself, another wave 
older by twelve hours, which has just made the entire circuit of Ireland. 
These two Avaves, united into one, take the common direction which re- 
sults from their original impulsion, and flow together into the Gulf of the 




Fig. 3S.— Tides of the English Chaunel. 

Severn. In the same manner, the tide which enters the Channel meets 
ofi" Jersey with another wave, Avhich has made the tour of the British Isles 
in twenty-four hours, and the two joining each other, dash their enormous 
liquid mass against the strand and rocks of Brittany. 

If two tides coming from opposite points, and ineeting at the time of 
high tide, are thus combined in one, they, on the contrary, neutralize and 
suppress each other, when the ebb of the one crosses the flow of the other. 
A phenomenon of interference occurs then comparable to that of two 
luminous vibrations extinguishing each other. Fitzroy was the first who 

*■ Marchal, Annales des Fonts et Chaussees, 1854. 

t See the section entitled The slow Oscillations of the Land. 



MEETING OF THE TIDES. m 

pointed out a rcg-ion of the ocean where contrary tides maintain the snr- 
Ihce of the water in equilibrium. This region is the estuary of La Plata. 
At sight of this gulf, which is no less than 15Q miles at the entrance, one 
Avould be tempted to believe that the amplitude of the ebb and flow would 
be as enormous there as in the Bay of Fundy or the Gulf of St. Malo. 
But, on the contrary, the tides there are scarcely any thing. The strong 
oscillations of the level that have been observed in that estuary are due 
almost wholly to the regular breezes and the tempests, which depress the 
Avaves on one side and raise them on the other. ^Then, too, as the land 
Avinds generally predominate during the morning, and are replaced in the 
evening by the sea-breezes, the ebb and flow, obedient to the alternating 
impulses of the atmosphere, succeed each other every twelve hours ; the 
tide rises in the afternoon and falls the next morning.* This apparent 
anomaly is easily explained by the meeting of high and low water at the 
entrance of the estuary. The tidal waves which flow to the south on the 
Brazilian side, and to the north on the side of Patagonia, do not strike the 
coasts at the same instant daily. They follow each other at an interval 
of several hours, and the lateral currents which diverge from tl\era suc- 
ceed one another at the mouth of the estuary of La Plata, so as to main- 
tain the liquid mass at nearly the same level. At the moment Avhen the 
ebb of the northern tide is about to occur, the southern flow takes place, 
the pressure of which, exercised in the contrary direction, prevents the 
waters from falling ; then, when a new tide from the coasts of Brazil pre- 
sents itself, the surface of the sea is already lowered in the southern lati- 
tudes. The swellings would intersect each other, and on the line of inter- 
ference the water would be subject to no oscillations. 

It is probable that to causes of a similar kind we must attribute the 
formation of those diurnal, and always very slight, tides which occur at 
the mouth of the Mississippi, on the coasts of New Ireland, at Port Dal- 
rymple in Tasmania, to the south of Australia, near King George's Gulf, 
in the Gulf of Tonquin, in the Bay of Bahr-el-Benat, in the Persian Gulf, 
in the White Sea, and in many other parts of the ocean. These slow 
changes of level, the ebb and flow of which each lasts twelve hours, pre- 
sent, like ordinary tides, the greatest diversity in their phenomena, ac- 
cording to the direction of the winds and the currents, the respective po- 
sitions of the sun and moon, and the parts of the sea where this equilib- 
rium of the waters is established. On the moving surface of the ocean, 
all the undulations, whatever may be their cause, are mixed and con- 
founded, and in this ceaseless changing and mingling of the waves it is 
impossible to discern, without long and patient research, the part taken 
by each agent in disturbing the perfect repose of the sea-level. The 
problem can be solved in a general manner only, without taking account 
of details that have been as yet imperfectly observed. Thus it is known 
that in the port of Vera Cruz and on the neighboring coast the winds 
have a marked preponderance, for they sometimes maintain the surfoce 
* Martin de Moussy, Confederation Argentine, t. i., p. 78. 



112 



THE OVEAK 



of the sea at the same level during whole days. At the mouths of the 
Mississippi, where the daily tide has a rise of little more than fourteen 
inches, it is not less regular in its progress* and its total height each day 
represents exactly the difference of level between the two composing- 
waves which have crossed each other. Finally, the tide at Tahiti, nearly 
twelve inches high, is the result of many more oscillations; for four tides, 




39.— Height of the Tides in St. George's Chaunel. 



TIDELSS AREAS IN THE SEA. 



113 



coming from the four cardinal points, meet each other there, all differing 
in their speed and their hour of high water. It is not surprising that, in 
the middle of this general intersection of the tides of the Pacific Ocean, 
that of Tahiti is almost completely neutralized.* 

The Irish Channel, so well studied by Beechey, presents a very curious 
example of a perfect equilibrium of waters, and that almost opposite the 
Bristor Channel, Avhere the sea rises and falls alternately above 48* feet. 
That part of the Channel whose surface remains at rest borders on the 
Irish coast not far from the little town of Courtown, to the south of Ark- 
low. There neither rise nor fall in the waters has ever been observed, 
though the currents of the ebb and flow run along the coast alternately, 
with a speed of nearly four and a half miles per hour. The point where 
the waters are always in equilibrium may be considered as a kind of 
" hinge " on which the tides turn. Their amplitude is greater and greater 
in proportion as they are distant from this tranquil region — to the north- 
east toward Holyhead and Liverpool, to the south-east toward Milford 
Haven and Bristol. In the North Sea, the aieeting of high and low 
water, nor far from the Straits of Dover, is marked by another centre of 
equilibrium, which seems to oscillate between the coasts of Holland and 
those of England, according to the atmospheric and marine currents, and 
the movements of the heavenly bodies. In this place Hewitt has ascer- 
tained that the tide rises two feet only ; and it is in this region, where the 
waters keep almost always at the same level, that the largest and most 
numerous sand-banks are deposited. 



ifours 



l cnv- waUr.levcl 




■^ The.hmmsS.6.j8.g.io,aarcrxufu»ved' 

Fig. 40.— Crossing of the Swellings of the Tides in the English Channel and the North Sea, from the 
Scilly Isles to the Mouth of the Humber. 

It appears that the two tidal currents which meet near the Straits of 
Dover — the one coming directly from the Atlantic, the other from the 
North Sea — do not follow the centre of the Channel, and consequently do 
not encounter each other directly. The rotation of the earth, which in 
the northern hemisphere displaces all moving bodies toward the right, 
causes each of the tidal waves to diverge in this direction. In the Chan- 
nel the tidal wave, which is directly propagated, constantly leans toward 
the right — that is to say, toward the south ; its force is, therefore, much 
greater on the coasts of France than on those of England, and when it 
has passed the Straits it keeps its preponderance on the coasts of the con- 
tinent as far as the mouths of the Meuse ; the tide coming from the north, 
* Fitzroy, Adventure and Beagle, Appendix to vol. ii., p. 290. 



114 THE OCEAN. 

on the other hand, deviates likewise to the right, and flows along the 
coasts of England. The crossing of these two contrary currents gives 
rise to numerous gyratory movements off* the coast of France and Great 
Britain, the incessantly changing curves of which form a veritable laby- 
rinth.* 

In the roadstead of Havre the meeting of the tides results in a remark- 
able phenomenon, which is at the same time one of the most useful for 
navigation. Instead of falling immediately after having attained its 
point of highest tide, the sea remains steady for three hours, and thus 
permits vessels to sail all over the road, and to penetrate with ease into 
the port, floating constantly over deep water. The seamen saw in this 
fact a sort of miracle, before its true cause had been revealed. When the 
tide from the Atlantic rolls toward the east to the middle of the Channel, 
it is arrested in its course by the peninsula of Cotentin, and can only ad- 
vance freely to the north of the Gulf, toward the mouth of the Seine. 
The marine level is thus more elevated at the centre than on its shores, 
and its waters are spread laterally toward the road of Havre and the 
other parts of the coast. At the time of low watei", when fhe ebb pre- 
vails in the centre of the Channel, the inclination is changed; but before 
the waters of Havre can descend toward the central course of the Chan- 
nel, which carries such an enormous mass of fluid to the ocean, they are 
kept back by the wave which, after having struck the Cape of Antifer, 
flows along the shores from north-east to south-west, to the Cape of La 
Heve. Then, when the force of this partial tide fails, another river-tide, 
which has followed the coast of ISToi'mandy from St.Vaast to Trouville, 
still maintains the level for a time.f 

In almost all river-ports, as we can easily understand, the ebb lasts 
longer than the flow, for the fluvial current neutralizes the tide during 
a shorter or longer period, and then, adding to the ebb, can not but 
augment its duration.^ A fact more difficult to explain is that, while in 
the greater number of ports remote from any river's mouth, the rising 
tide is shorter than the falling, numerous instances of the opposite are to 
be seen ; and especially the port of Holyhead. According to the hypoth- 
esis generally adopted, this longer duration of ebb ought to be attributed 
to the rotation of the earth in the direction of west to east. The tidal 
wave being propagated in the contrary direction — that is to say, from east 
to west — would meet a certain resistance in the waters which are spread 
before it. It would rise up, and become steeper and more rapid toward 
the west ; while its other slope, that of the ebb, would lengthen itself to- 
ward the east. This will explain why the phase of the flow does not last 
so long as that of the ebb. 

The inequalities which are observed in certain parts between two suc- 
cessive tides are likewise a strange and, in some respects, unexplained 
phenomenon. These various inequalities, now in the duration, and now 

* Annales des Fonts et Chaussees, 1863, first week. 

t Baude, Revue des Deux Mondes. t See p. 121. 



INEQUALITIES OF THE TIDES. 115 

in the respective heights of the two tides of morning and evening — or 
which even aifect every oscillation in its entire course — arise in part 
from the declination of the moon ; that is to say, from its varying distance 
to the south or north of the equinoctial line. But in many cases the dii- 
ferences between two successive tides are relatively enormous, and this 
explanation is not sufficient. Thus at Port Essingtou, on the northern 
coast of Australia, differences in height of nearly four feet between thf 
oscillation of evening and morning have been observed. At Singapore, 
where the mean tide during the time of highest water is ilearly seven 
feet, the difference between two succeeding tides is sometimes nearly five 
feet. At Kurrachee the daily variation is no less, and in the Gulf of Cam- 
bay it attains to nearly seven feet. At Bassadore, at the entrance of the 
Persian Gulf, the duration of one oscillation of the sea sometimes exceeds 
by two hours that which follows it ; and, finally, it has happened at Pe- 
tropaulowski, in the Northern Pacific, that expected tides have never ap- 
peared at all. » We can explain these singular anomalies only by the in- 
tersection of several reflex waves, diurnal and semi-diurnal, which interfere 
with one another ; and the confused oscillations of which are produced by 
the meeting of moving liquid masses of diverse origin. It is thus that on 
the surface of a jjond, the waves that have risen at dj^erent points form 
an immense' net- work of intersecting lines, which the breeze mingles in 
undecided wavelets. 



116 THE OCEAN. 



CHAPTER XIV. 

TIDAL CURRENTS. T-EACES AND WHIRLPOOLS. — TIDAL EDDIES. — RIVER TIDES. 

The popular belief is that the oscillations of the tides are always ac- 
companied iby currents changing regularly with the ebb and flow, and 
tending alternately in one direction or the other. This is, it is true, a 
pretty frequent phenomenon, especially at the mouths of rivers. Usually, 
when the- water rises, a tidal current rushes at the same time toward the 
shore and into the estuaries of rivers ; then, when the level of the liquid 
mass falls, a return or low-water current, swelled by the fresh water from 
inland, flows again toward the open sea. Nevertheless, this coincidence 
of the horizontal currents with the vertical oscillations of the ocean is far 
from being reproduced with regularity in all parts. The tide, being mere- 
ly a swelling of the sea, can rise without the least movement occurring in 
one direction or the other. A remarkable example of this is seen in the 
Irish Sea, so rich in maritime phenomena. In the middle of the channel 
which separates the Isle of Man from Ireland, the sheet of *water keeps 
perfectly tranquil between the contrary currents, though the water at 
this place rises more than eighteen feet during the spring-tides. On the 
other hand, as one can see at Courtown, on the coast of Arklow, the cur- 
rent determined by the meeting of opposing tides can have a great speed 
where the surface of the sea neither rises nor falls,* Finally, the same 
wave can follow a constant direction across two contiguous regions of 
the sea, one of which is at ebb and the other at flow. 

The currents which occur in straits in consequence of differences of lev- 
el are sometimes extremely violent ; and by their abrupt changes, their 
eddies and whirlpools may be classed among the most dangerous' phenpm- 
ena of the ocean. Thus the entrance to the Gulf of Normandy and the 
Channel Islands is rightly dreaded by navigators because of the terrible 
speed which the tidal currents attain there. The Blanchard Race, a 
strait w hieh separates the Cape of La Hogue from the Island of Alderney, 
is the fi^^ of these terrible marine defiles where the ebb and flow, re- 
strained between chains of xock^ and shallows, move at the time of high 
water with a speed of nearly ten miles per hour. Then comes the strait 
which bears the significant name of the Deroute Passage, and in which the 
currents flowing along the rugged western coast of Cotentin meet those 
which come directly from the open sea by the! breach opened between 
the islands of Jersey and Guernsey ; there the marine rivers, less rapid, 
are nevertheless animated by a speed of nearly ten feet per second. f 
Since the disaster of La Hogue, where Tourville, unable to sail against 
the formidable current of Blanchard Race, lost so many of his ships, how 

* See p. 113. t Mounier, Memoire sur les Courants de la Manche. 



TIDAL CURRENTS. 



m 



many vessels have been wrecked, how many crews have perished, in 
these terrible straits, which Victor Hugo has chosen as the theatre for his 
t^loomy drama of "The Toilers of the Sea!" 




Fig. 41.— Course of the Tide in tlie Irisli Sea. 

The mariile defiles which separate the British Isles from the continent, 
and especially those of the Hebrides, the Orkney, the Shetland, Faroe, 
and Lofoten Islands (whose rocks and shelving banks confusedly stud a 
very uneven sea-bed, full of abysses), are also traversed by alternate tid- 
al currents all the more rapid and tumultuous, because of the difference 
of level between the two sheets of water which meet in the strait. The 
most formidable of these passages is perhaps the Great Gulf, or " Coire- 
bhreacain,"* between the islands of Jura and Scarba, on the western coast 
of Scotland. At each change in the tide a current, flowing alternately 
* Gaelic, "Caldron of the Snotted Seas." 



118 THE OCEAN. 

toward the main-land and toward the open sea, is produced. The English 
Admiralty chart estimates its speed at nearly eleven miles per hour, but 
sailors affirm that it is at least nearly twelve and a half miles — that is 
to say, more rapid than the stream of any continental river. No vessel 
can venture, in strong tides, into such a terrible race ; especially when 
the wind blows in the contrary dii-ection to the tide, for the Coirebhrea- 
cain is then in its entire extent a foaming " caldron," without any visible 
limits.* 

Other tidal conflicts are hardly less terrible ; such, for example, is that 
observed in the straits of the Pentland Firth, between Scotland and the 
Orkneys, and which ends in the formation of currents estimated at more 
than ten'miles per hour. But the most celebrated of all these encounters 
between two tides .of different levels is the Moskoestrom, toward the 
southerly extremity of the archipelago of the Lofoten Islands, called also 
by seamen the Maelstrom. The sombre imagination of northern peoples, 
always tending to the creation of monsters, saw in the strait of the Mos- 
koestrom a polype Avith arms several hundred yards in length, which 
caused the waters to whirl in an immense eddy, in oi'der to draw ships 
into it and ingulf them. From this ancient legend there has even re- 
mained with many the idea that this cun-ent is a sort of abyss in the 
form of a funnel,.which floating objects approach by degrees, forming 
narrower and narrower circles, till they finally plunge forever into this 
revolving well. But it is nothing of the sort. The only eddies are. small 
lateral ones, produced by the meeting of the cui'rents, and hardly two or 
three yards deep. The principal phenomenon consists, as in the Coire- 
bhreacain and the Blanchard Race, of a rapid movement of the waters 
tending ■ alternately in one or the other direction at the time of the 
change of the tides. When in the open sea the flow rises in the direction 
from south to north, a part of its mass spreads with force into the strait 
opening to the south, between the two islands of Moskoe and Moskoe- 
naes. In proportion as the surface approaches a state of equilibrium, the 
current, gradually weakened, tends toward the south-west, and then to 
the west. A period of calm follows these different movements of the 
waves when the level is perfectly established; but soon the ebb com- 
mences, and tends in an inverse direction, at first toward the north, then 
toward the north-east and east. Thus, in the space of one tide the waters 
are alternately carried, though with varying force, toward all the points 
of the compass. 

The tidal currents, which occur at the entrance to rivers, frequently 
give place to tumultuous movements less terrible, it is true, than those 
of the races in archipelagoes, but sometimes of an equally striking as- 
pect. These phenomena are known under the name of the " bore," barre, 
" eager," or mascaret. 

In penetrating into the estuary of a river, the tidal wave, retarded by 
the shallows, and narrowed by its banks, must necessarily swell, because 
* AthencEum, August 26, 1864; Mittheilungen von Petermann, t. ix., 1864. 



Rimil OF THE TIDE UP lilVEIiS. II9 

of the restriction of the liquid mass in its bed. All the inlets and bays 
into which the tide penetrates present thus the spectacle of the "bore;" 
but in many passages the regular inclination of the bed, the uniformity 
of the shores, or else an intersection of various currents, diminish the first 
undulation of the tidal wave, or permit it to be confused with other ir- 
regularities of the surface. Elsewhere, on the contrary, all the topo- 
graphical conditions are found united to give a great height to the 
" bore," and it then rises, like a moving wall, from one shore to the other 
of the estuary. At the mouths of certain rivers, such as the Amazon, the 
Hooghly, the Seine, the Dordogne, the Elbe, and the Weser, the waves of 
the "bore" assume enormous proportions at the tirne of high tides, and 
become formidable phenomena. In the Amazon, the " bore," called poro- 
roca because of the roaring of its waters, rises, it is said, in three success- 
ive waves, attaining together from thirty to fifty feet in height ; and ves- 
sels surprised by this sudden flood are in great risk of capsizing, as in the 
open sea. 

At the mouth of the Ganges the " bore" is also very formidable. As 
the old Hindoo legend says, in symbolic language, Bagharata having 
taken the divine (jranga as his spouse in the midst of snows, raised her in 
his arms, and, mounting his chariot, traced with its two large wheels the 
banks of the wide bed of the goddess. But, when they arrived at the 
sea-shore, Ganga recoiled with aff'right before the impure and monstrous 
ocean ; she fled abruptly by a thousand channels, and since that epoch 
she comes and goes by turns, now venturing to descend, and now fleeing 
again toward the mountains, twice a day.* 




Fig. 42.— Profile of a Tidal Wave observed iu the Bay of tlie Seine (after M. Partiot)j» 

It is in the bay of the Seine that the mascaret, or " eager," has been 
most regularly and carefully observed. Flowing from the open sea with 
a speed of from fifteen to twenty feet per second, the liquid wall remains 
curved toward the centre, under the pressure of the fluvial current. The 
two points of the enormous crescent break in foam on the shores; while 
in the middle of the concavity, the even, rounded wave advances without 
even rippling the water before it. It seems to turn on the river like a 
gigantic serpent ; rising from six and a half to ten»feet above the liquid 
plain ; while behind it rise waves or eteules in concentric undulations 
quite as high, the advanced guard of the tidal mass. All the obstacles 
placed in the way of the mascaret irritate it by increasing its impetus; 
at length the tide, entering a wider and deeper part of the bed, gradually 
calms and moderates its height till it meets with another shallow or 
promontory. Moreover, each tide-wave is distinguished from the pre- 
* Carl Ritter, Von Hoff, Verdnderungen der Erdoberjidche, t. i., p. 378. 



120 



THE OCEAN. 



DiJce Korfh 




Fig. 43.— Height of the " Mascaret," or Tidal Wave, observed between Caudebec and Meilleraye 

(after M. Partiot). 

ceding by reason of the difference of winds, currents, and the masses of 
water put in motion. There is nothing more curious than to see, from 
the height of a promontory, two waves repelled obliquely by the banks 
crossing their furrows, and their eteules. 



Fig. 44 Plan of the 




ivscaret," or Tidal Wave, observed in the Narrows of the Seine (after 
M. Partiot). 



The sole means of diminishing the force of the masearet, which in sev- 
eral estuaries, and especially in the bay of the Seine, is sometimes danger- 
ous to small vessels, is to regulate the channel by deepening the shallows 






X 



,^: 



/'■ 



Pig. 45.— Plan of two Tidal Waves crossing each other's course on the Banks of the Bay of the Seiuc 

(after M. Partiot). ' 

and straightening the banks. The works, which insure a freer and deeper 
channel for navigation, are those which prevent the injuries caused by 
the great violence of the tidal waves.* The mascaret of the Seine disap- 
peared recently for some years, owing to the elevation of a bank of sand 
* Partiot, Annates des Fonts et Chaussees, t. i., 1861, 



EFFECT OF THE TIDES OH BIVERS. 



121 



like a dike, which prevented the entrance of the tide into the bed of the 
river. The encounter of the mascaret and the fluvial current have again 
raised this bank of sand at a little distance. On striking against this 
new obstacle, the tidal wave rises up to surmount it. Different hydraulic 
works, undertaken in the beds of the Garonne and the Dordogne above-the 
Bec-d'Ambez, have also often modified the phenomena of the mascaret there. 
The sudden appearance of the tide in estuaries raises the fluvial waters 
very rapidly from the level of low to that of high water. At Tancarville, 
which is the precise spot where the Seine discharges itself into the bay, 
and where the tide exceeds a mean amplitude of about thirteen feet, the 
entire rising of the waters is accomplished in two hours, while the fall of 
the liquid mass, driven back by the tide, occupies about ten hours. The 
river having to discharge during the period of ebb not only that Avhich 
the flow had brought to it, but also the fresh waters from higher up, 
must follow its normal course toward the sea during a space of time 
longer than that in which it is driven back by the rising tide. For each 
point of the river-bed the duration of. the flow is generally the shorter 
the farther that point is from the sea: the force of the tide is gradually 
exhausted, and toward the end of its course it only momentarily retards 
the speed of the fluvial current. 



^ 






0° S 



jm^. 



-5=iS2 



7y^ 
4y^ 



Fig. 46.— Tides of the Garonne. 



The amplitude of the tides diminishes, likewise, in proportion to their 
progress up the stream in rivers. The mass of fresh water flowing inces- 
santly within the channel prevents the low tide from sinking, as it does 
on the sea-shore ; and as to the high tide, its shorter duration does not 
allow it to rise to a much higher level than that which it attains on the 
strands and cliffs by the ocean. Thus, in the Garonne, the difference be- 
tween the ebb and flow diminishes gradually above the Bec-d'Ambez; 
and near Castets, at about ninety-five miles from the sea, it is finally re- 
duced to zero. In certain places, it is true, particular circumstances may 
cause apparent exceptions to this general law ; a promontory rising be- 
fore the tidal wave like that of Tancarville, in the bay of the Seine, bars 
the way to the marine waters, and gives them, in consequence, a greater 
relative height above low water. But in spite of these abrupt projec- 
tions, the mean amplitude of the tide diminishes from the lower to the 
upper course, and finally it becomes imperceptible. 



122 THE OCEAN. 



CHAPTER XV. 

EBB AND FLOW IN LAKES AND INLAND SEAS. — CUEEENTS OF THE EUEI- 
PUS. — SCYLLA AND CHAETBDIS. 

The attraction of the sun and moon acts no less on inclosed seas than 
on the great ocean; but in basins of small extent the tide has not the 
necessary space to rise and develop itself in an appreciable manner. 
Lake Michigan, whi®h, although not less than 56,000 square miles in. ex- 
tent, is the smallest surface we are acquainted with where the regular 
return of the ebb and flow have been established with precision ; the am- 
plitude of the tide there is, according to Lieutenant Graham, less than 
three inches. Still, it is undoubted that the smaller lake basins also 
experience normal oscillations every twelve hours : measures carefully 
made will probably reveal them one day. 

Even in the vast Mediterranean the tides are very little perceived, ex- 
cepting in the Gulfs of Syrtes, between the ancient Pentapolis and Tunis. 
In this part the phenomenon of the ebb and flow occurs with the greatest 
regularity, and one can study its progress as in the ocean. At the mouth 
of Oued-Gabes, almost at the end of the Lesser Syrtes, the water alter- 
nately rises and falls at least six and a half feet. More to the north, in 
the port of Sfax, the average difference between high and low water is 
about five feet, but at the epoch of the equinoxes this difference attains 
to nearly eight feet. Finally, at the Island of Djerbah, the ancient island 
of the Lotophagi, the mean amplitude of the tide is not less than nine 
feet ten inches.* This remarkable height of the tide on the shores of the 
Syrtes doubtless arises from the Mediterranean presenting in its southern 
part, from Port Said to Ceuta, a single basin, with a slightly sinuous 
bank, while on the coast of Europe it is divided into a number of smaller 
seas, those of Sardinia, the Adriatic Gulf, the Ionian Sea, and the Archi- 
pelago. Besides, the winds being much more regular on the African 
coast, the alternate play of the tides is not disturbed there, as on the 
coasts of Europe, which belong to the zone of variable winds. 

However, an attentive examination of the movement of the waves has 
equally revealed to observers the existence of the tidal wave in the par- 
tial basins of the northern shores of the Mediterranean. Beyond Malaga, 
where the tides of the Atlantic are still propagated, the level of the sea 
hardly changes ; but on the coasts of Italy the oscillations begin to be 
perceptible again. At Leghorn, the tide rises less than twelve inches ; at 
Venice, the difference between the high and low Avaters varies from one 
to three feet.f At the mouths of the Po the tide does not attain the same 

* Victor Guerin, Voyage Archeologique en Tunisie, 1. 1. 
t G. Collegno, Geologia delV Italia, p. 280. 



CURRENTS OF THE MEDITERRANEAN. 123 

height. On the coasts of Zante, in the Ionian Sea, it is less than six inch- 
es ; tiually, at Corfu, it does not exceed an inch.* In the Oriental basin of 
the Mediterranean, the tide is likewise very slight; nevertheless, the al- 
ternate osciiration of the sea is not ignored by the people living on the 
'shores. Omar spoke, doubtless, of the tide when he said, " The sea stands 
very high, and day and night it entreats the permission of God to inun- 
date the land." 

Not only has the Mediterranean its ebb and flow like the ocean, but it 
has also its currents and eddies, and among these phenomena there are 
some which, without being as formidable as the Moskoestrom or Blanch- 
ard Race, are not less celebrated, because of the glory with which clas- 
sical antiquity has invested them. Thus the Euripus, or Strait of Egripos, 
which separates the Island of Negropont from Continental Greece, is said 
to be traversed by extraordinary currents, which produce with regularity 
their surprising phenomena. Up to the eighth day of the lunar month, 
the ebb and flow, whose mean amplitude is less than a foot, follow one 
another in a normal manner, only Avith one hour's delay ; but from the 
ninth to the thirteenth day the movement of oscillation is suddenly has- 
tened, and during the twenty-four hours no less than twelve, thirteen, or 
fourteen tides may be counted, each one having its flow, its period of 
stability, and its ebb. From the fourteenth to the twentieth day a nor- 
mal state of things prevails ; then, from the twenty-first to the twenty- 
sixth, everj^ day will again be marked by a series of a dozen high and 
low tides. Such is the result of the experiences of the millers, who see 
the wheels of their mills turn alternately one way and the other, accord- 
ing to the direction of the current. f On their side, the Mussulmans main- 
tain, as an article of faith, that the five waves of the Euripus regularly 
follow the five hours of prayer ;J finally, the rapid observations of several 
travelers describe in still another manner the oscillations of the sea in the 
narrow channel. The fact is, that the currents of the Strait of Negropont 
are unexplained, and if they succeed one another in as strange a mannen 
as the inhabitants of those shores affirm, one would really comprehend 
the legend, according to which Aristotle, after having vainly sought to 
divine the mystery, plunged in despair into the whirlpools of the EurijDUS. 

Still more famous than the currents of the Strait of Euboea were the 
abysses of Scylla and Charybdis, braved for the first time by the wise 
Ulysses. According to the Homeric chants, the two howling monsters 
which guarded the entrance to the Straits of Messina drew into their 
submarine caverns immense whirlpools of water, which they afterward 
discharged in furious currents, and all the ships which approached those 
formidable caverns were inevitably ingulfed. At present there are no 
straits in the Mediterranean more frequented than those of Messina, and, 
owing to the soundings effected in these pretended abysses where the 
ancients saw the navel of the sea, the monsters have lost their terrible 

* Von HofF, Verdnderungen der Erdoberfldche, t. iii., p. 256. 

t Berghaus von Kloden, Handbuch der Erdkunde. % J^atur, t. viii., 1864. 



124 THE OCEAN. 

prestige. It is now known that the whirlpools of Charybdis and Scylla 
are nothing else than lateral movements produced by the ebb and flow, 
in their passage through a too narrow channel, whose width is hardly two 
miles, and which the conquerors of Sicily have more than once crossed by 
swimming on their horses. At the time of the rising tide the isurrent 
tends to the north, from the Ionian to the Tyrrhenian sea ; at the fall of 
the tide, the stream coming from the north assumes the preponderance, 
and drives the contrary current toward the south.* But there is a strife 
between the two liquid masses, and the field of battle moves incessantly 
from Messina to Scylla. On the confines of the currents, where the min- 
gling of the waters is effected with violence, narrow eddies are formed, 
where the waves are more agitated than elsewhere; these are the "eye- 
lets," or garofali. Ships avoid them, for fear of being too violently shaken ; 
but they run no danger unless the wind blows strongly in a contrary di- 
rection to the tide. The strait is a curious spectacle, seen from the height 
of the mountains of Messina or Reggio, with the undulations and eddies 
that the conflicting waters describe ; every instant sheets of water of a 
darker tint than those of the surface are seen to change their form, in- 
dicating the ebb and flow. 



SidKa'^ I ^. ^. ^^ ^ CalabrG 

CO 



Mg. 47. — Profile oi ihe MiaiN ol Ivle^sina. 

In the other inclosed seas of Europe the tides are likewise little felt. 
They are less than sixteen inches on an average in the Zuyder Zee, and 
during the days of the equinox or of tempests they hardly attain three feet 
six inches. The Baltic, which is much narrower, and more strewn with 
islands than the Mediterranean, is subject in consequence to much slighter 
oscillations ; it was even called in former times morimarusa {mor y marb) 
— that is to say, in Celtic language, "Dead Sea."f The sailors pay no at- 
tention to the variations of the surface produced by the ebb and flow : 
for them the winds, the currents, and the meteorology of the atmosphere 
are the only phenomena which they have to observe. In fact, on the 
western coast of Jutland the tide is on an average less than twelve inch- 
es;- at the entrance to the Categat it loses still more in force and regu- 
larity ; and in the straits of the Sound and the two Belts it is difficult to 
recognize. In the harbor of Copenhagen an oscillation of about one or 
two inches can still be sometimes distinguished, but only when the w^eath- 
er is perfectly calm and the surface of the water hardly rippled. At Wis- 
mar the phenomena of the tide are still more uncertain ; and it is only by 

* Spallanzani; Von Itoff ; Smyth. t Von Maack, Zeitschrift fur die Erdhmde, I860. 




DIFFERENCE IN TIDES. 125 

a series of observations on the surface of the Avaters pursued during sev- 
eral years that the probable existence of a total variation of little more 
than three inches between high and low water can be ascertained. Near 
Stralsund the difference is only one and a half inches, and near Merael it 
hardly exceeds an inch. The much more considerable variations which 
occur in the level of the sea arise from the winds, the currents, or the 
pressure of the atmosphere. Rapid oscillations of nearly three feet have 
been sometimes seen to occur ; but these are the seiches, similar to those 
of the Lake of Genoa.* The force of the winds alone is sometimes suf- 
Hcient to lower by little more than three feet the level of the sea in cer- 
tain straits, as well as in the gulfs of Esthonia and Finland.f 

The laws of the phenomena of the mouths of rivers difler entirely in the 
seas with strong tides, as the Northern Atlantic, and in those with insen- 
sible oscillations, like the Baltic and the Mediterranean. L> the estuaries, 
where the sea rises regularly twice a day to a great height, it passes over 
every obstacle, bars, or sand-banks accumulated at the entrance to the 
mouths of rivers ; while in those places where the level of the sea remains 
always the same, the dikes of mud or sand dej^osited parallel to the coasts 
between the fresh and salt waters always close the entrance^ the river. 
Thus the Rio Magdalena and the Arato, in the Antilles ; the Rhone, the 
Po, and the Nile, in the Mediterranean, spread their liquid mass over bars 
which are often hardly a yard at the lowest part ;J while the river of the 
Amazons, the St. Lawrence, the Gironde, and the Thames, allow free pas- 
sage to ships at all hours. 

This diversity of fluvial laws, according to the height of the oscillations 
of the tide, has the most important consequences for the commerce of 
regions watered by great rivers. In general, the ports of the rivers with- 
out tide can not be established at the mouth itself, because of the want 
of water, and merchants are obliged to choose a locality situated on the 
sea-coast at a certain distance from the sandy mouths of the river for 
tfieir emporiums. Thus Marseilles, Avhere almost all the commerce of the 
great basin of the Rhone is transacted, is constructed on the shores of a 
deep bay of the Mediterranean, far from the peninsulas of mud between 
which the river discharges itself Alexandria, the great port of the Egyp- 
tian delta, lies to the west of the alluvial delta of the Nile ; Venice is far 
from the mouths of the Po ; Leghorn protects its port from the approach 
of the Arno ; Barcelona is not at the entrance to the Ebro ; and Cartha- 
gena, in the West Indies, and Santa Maria are only in communication with 
the great Magdalena by means of hardly navigable canals. The excep- 
tions to this rule ai*e not very numerous ; still we may cite Dantzig on 
the Vistula, Stettin on the Oder, and Galatz on the Danube. § 

In seas with high tides the principal ports are found, on the contrai'v, 

* See the chapter entitled Lakes. 

f Von Sass, Bulletin de rAcadeinie de St. Petersbourg, t. viii., 6. 

t See the chapter entitled Rivers. 

§ Ernest Desjardins, De l embouchure du Rhone. 



126 THE OCEAN. 

not on the maritime coast-line, but on the rivers, and even at a certain 
distance from the mouth, not far from the place where the tide rises twice 
a day, thus changing the river into a true maritime gulf. London, Ham- 
burg, Nantes, Bordeaux, Rouen, and many other great commercial cities, 
have been gradually built, in consequence of the necessities of commerce^ 
as far as possible inland at the precise spot where the depth of water and 
the force of the tide allow ships to approach easily. Nevertheless, since 
the ships of the present day draw much more water than those of our 
ancestors, the result is that a number of ports on rivers have become in- 
sufficient. It is thus that Rouen has been gradually replaced by Havre 
as the port for international commerce. Thus Nantes, too, has. seen in 
these days a rival city grow up in the village of St. Nazaire, so modest 
but a few yeai'S ago. Perhaps the hamlet of Verdon, provided sooner or 
later with docks, basins, and jetties, will become likewise the real com- 
mercial Bordeaux. 



DEPOSITS AT TUE BOTTOM OF THE SEA. i27 



BOOK IV.— THE SHORES AND ISLANDS. 



CHAPTER XVI. 

INCESSANT MODIFICATIONS OF THE COAST LINE. — THE FIORDS OF SCANDI- 
NAVIA AND OTHER COUNTRIES NEAR THE POLES. 

The sea, every wave of which contains perhaps thousands of living 
organisms, seems itself to be animated by a vast and mighty life. Ever- 
changing hues, dark as fog o^ brilliant as the sun, pass over its immense 
extent, its surface ripples in long undulations, or rises in bristling waves ; 
its shores are touched with a border of foam, or disappear under the 
white mass of breaking surf Sometimes it breathes a scarcely audible 
murmur, and again it combines in very thunder the roarings of allots 
waves dashed and broken by the tempest. By turns it is smiling and 
terrible, gracious or formidable. Its aspect fascinates us ; and as we 
walk along its shores, it is impossible to avoid contemplating and inter- 
rogating it ceaselessly. Ever moving, it symbolizes life, in distinction 
to the silent and passive earth which it assaults with its waves. And 
besides, is it not always untiringly at work to modify the contour of the 
continents, after having once formed them layer by layer in the depth of 
its waters? 

The most important part of the geological labors of the ocean is hid- 
den from our eyes ; for it is at the bottom of its abysses that the sea de- 
posits the silica, limestone, chalk, and conglomerates of every kind which 
will one day constitute new lands. But at least we can witness the con- 
tinual modifications to which the incessant movement of the sea subjects 
the shores. These modifications are considerable, and during the his- 
torical ages a number of coasts have already completely changed their 
form and aspect. Promontories have been razed, while at other parts 
points have advanced into the waves ; islands have been transformed 
into reefs; others have been entirely swallowed up; others again joined- 
to the main-land. The sinuous line of the shore has not ceased to oscil- 
late, encroaching here on the waters of the ocean, and there on the con- 
tinental surface. The action of the sea is double ; it is constantly re- 
touching the contours of its basin, either by wearing away the rocks that 
border it anS carrying away the strand, or by casting uj) on its coast the 
alluvium and wreck of every kind that it tosses in its waves. All that 
it ingulfs on one side it gives back elsewhere under another form. 

Before the sea had modified its shores by destroying peninsulas and 
filling up bays and estuaries, the form of the coast was certainly much 



128 



THE OCEAN. 



less regular than it is now in the outline of most countries. If the ma- 
rine waters were raised by a sudden revolution to 100 or 200 yards 
above their present level, the ocean, inundating all the river valleys to a 
very great distance from the present shores, would suddenly enter in 
elongated gulfs into the depressions of the continent, and change. all the 
valleys and lateral gorges into bays. In the place of each of those river- 
mouths which hardly indent the normal line of the coast, deep hollows 
would be opened, dividing into numberless ramifications. But a work in 
the opposite direction will instantly be commenced when this change in 
the outline of the shores is accomplished. On the one side, the water- 
courses, bringing down their alluvium, will gradually fill the upper val- 
leys, and little by little restrict the domain of the maritime conquests. 
On the other side, the ocean will also labor by its dunes along the coast, 
its banks of sand or shingle, to take away from its surface all those new 
bays that the sudden increase of its watei^s had given it. After an in- 
definite lapse of centuries, the shore would finally re-assume the gently 
undulated form that the greater number of coasts now present. 




Fig. 48. — Lysefjord, Norway. 

There are still many counti'ies where this double work of the sea and 
the continental waters has hardly commenced. Those lands whose coast- 
line, thus preserving its first form, is still deeply indented, are all situated 
•at a great distance from the equator, in the neighborhood of the Polar 
zone. In Europe, the western coasts of Scandinavia, from the promontory 
of Lindesnaes to the North Cape, are jagged by a series of these j^'ort?^,* 
or ramified gulfs, and not only the shore of the continent, but all those isl- 
ands also which form a sort of chain parallel to the Norwegian plateau, 
are fringed with peninsulas and cut into by small fjords, winding in im- 
mense passages. Among these indentations, which increase the length 
of the coast tenfold, and give to the coast-line a border of innumerable 
peninsulas, more or less parallel, some are pretty uniform in aspect, and 

* Called in Scotland ^ri/is. 



SEA-LOCHS AND FJORDS. 



129 



resemble enormous trenches, hollowed out in the;^thickness of the conti- 
nent ; others are divided into several lateral fjords, which make the in- 
land waters an almost inextricable labyrinth of channels, straits, and 
bays. The total development of the coasts is so much increased by these 
indentations, that the western shore of the peninsula, whose length in a 
straight line is about 1180 miles, is increased to above 8000 miles by the 
bends and turnings of the shore, Avhich is more than the distance from 
Paris to Japan. 



ChrLitiausliaai 




'/ 



•^i^le-Jjordy 



Fig. 49.— Fjords of Greenland. 

The plateaux of Scandinavia, terminating abruptly above the North 
Sea, the slopes which command the somljre defiles of the fjords, are al- 
most always very steep; there are some which rise in perpendicular or 
even overhanging walls, serving as a pedestal to high mountains. It is 
thus that the Thorsnuten, situated to the south of Bergen, on the shores 
f)f thg Hardanger Fjord, attains an elevation of above 5250 feet at less 
than two and a half miles from the shore. In many a bay of Western 
Norway cascades are seen to leap from the top of the cliff, and precipi- 

9 



130 



THE OCEAN. 



tate themselves in onejet into the sea, so that vessels can glide between 
the walls of the rocks and the parabola of the roaring cataracts. Below 
the water the escarpments are continued also in most of the gulfs, so 
that in certain defiles of rocks, whose breadth from cliif to cliif is only 
from 300 to 600 feet, the lead must be thrown to a depth of from 272 to 
32*7 fathoms before touching the rocky bottom.* In the " Toilers of the 
Sea," Victor Hugo correctly cites the Lysefjord as most fearful to con- 
template among its gloomy approaches, many of which are forever de- 
prived of a ray of sun by the high walls of rocks which inclose them. 




Mouths of Cattaro. 

This enormous putting, of an almost perfect regularity, penetrates above 
26 miles into the interior of the continent, though in several places it 
hardly exceeds 1965 feet in breadth; its walls rise to 3270 and 3600 
feet in height, and near the edge the lead only touches the ground at 
about 220 fathoms.f Doubtless the first seaman who sailed over the 
dark, tranquil waters of this abyss must have advanced with a sort of hor- 
ror, asking at each new turn of the approach whether he was not going 
to see some terrible god rise before him. Even now it is not without a 
shudder that one penetrates into this gloomy defile, where the ancients 
would doubtless have seen the entrance to the infernal regions. ^ ' 

* Berghaus, Was man von der Erde weiss, p. 280. 

t Vibe, Kiisten und Meer Norwegens, Mittheilungen von Petermann, 1860. 



FJOBDS OF SOUTH AMERICA. 



131 



The islands of Spitzbergen, Faroe, and Shetland present also in their 
outline hundreds of fjords, like those of Scandinavia. The coasts of Ice- 
land, Labrador, and Western Greenland, those of the islands of the Polar 
Archipelago, and finally the American coast-line of the Pacific, from the 
long peninsula of Alaska to the labyrinth of Vancouver's Islands, are no 
less rich in indentations than the coast-line of Norway. The shores of 
Scotland are deeply cut in the same way, but only on the western side, 
where there are besides numerous islands reproducing in miniature the 
maze of promontories and bays of the main-land. That part of Ireland 
turned toward the open sea develops itself also into a succession of rocky 
peninsulas, separated by narrow gulfs; but to the south and east the 
coasts of the British Islands are much less varied, in form, and sweep in 
long, regular curves. In France we hardly find a vestige of indentations 
like those of the Norwegian fjords, except at the extremity of Brittany ; 
and ther.e does not even exist a word in the language to designate them. 




Fig. 51.— Fjords of South America. 



In Spain, in the same way, the part of the peninsula turned toward the 
north-west, and where the ports of Ferrol and Coruiia open, is the only 
one which presents some lines of fjords half filled up. Two countries on 



132 THE OCEAN. 

the borders of the Mediterranean have their coasts also cut into fjords, 
partially obliterated by alluvium; these are Asia Minor and Dalmatia, 
whose high mountains, formerly covered with glaciers, overlook narrow 
bays with fantastic outlines like the mouths of Cattaro ; but along these 
two shores the peninsulas of the coast-line are still uaiformly turned to- 
ward the west. 

To the south of the Adriatic and the Archipelago, on the coast-line of 
warm or torrid countries, no more fjords are seen. To find a similar 
formation of shores we must traverse the entire continent of America to 
its southern extremity. The fjords only commence beyond the uniform 
coast-line of Chili, with the Island of Chiloe, its numerous bays, and the 
net-work of straits in the Archipelago of Magellan and Terra del Fuego. 
This is the only region in the southern hemisphere where the astonishing 
phenomenon of tortuous and deep valleys filled by the waters of the sea 
is witnessed. As to the countries of the Antarctic continent, no inden- 
tations can be recognized in them, since the contours of the bays and 
capes, the gulfs and peninsulas, are all filled by the snouts of glaciers and 
by continuous ice-fields. 



FILLING UP OF FJORDS. 133 



CHAPTER XVII. 

FILLING UP OF THE FJORDS BY MARINE AND FLUVIAL ALLUVIUM. 

The comparative study of all the shores leads thus to the confirmation 
of this fact, that fjords are only met with on the coasts of cold countries, 
and tl]§,t, with equality of temperature, they are much more numerous 
and better developed on the western coasts than on those turned to the 
east. Why does this strange geographical contrast occur between the 
various shores, according to the position which they occupy to the north 
or south, to the west or east? Why have the strands, and even the cliffs, 
bathed by a warm or temperate atmosphere, assumed in the outline of 
their curves such a great regularity, while the valleys, opened in the 
thickness of the plateaux of Scandinavia, Greenland, and Patagonia, have 
preserved their primitive form? A cause whose effects are produced 
at the same time and in the same manner at the two extremities of the 
continents, in the northern islands of America and Europe and in the 
Magellanic Isles, must necessarily have been a great geological phenome- 
non, acting during an entire age of our planet. 

This phenomenon was the special climate which during the glacial pe- 
riod made itself felt on the surface of the globe, and transformed the 
mountain snows into long.rivers of ice. The map speaks for itself, so to 
say ; it relates clearly how the fjords, those ancient indentations of the 
coast-line, have been maintained in their primitive state by the prolonged 
sojourn of glaciers.* In fact, the cold period, the unequivocal witnesses 
of which are still to be seen even in the tropics and under the equator, at 
the foot of the Andes and in the valley of the Amazon, naturally lasted 
longer in the vicinity of the poles than under the torrid zone, and in the 
temperate regions. This glacial period, which terminated perhaps thou- 
sands of centuries ago on the burning shores of Brazil and Colombia, has 
ceased at a relatively recent epoch on the coasts of France and England. 
At an age still nearer our historical time, the fjords of Scandinavia have 
been in their turn freed from the glaciers that filled them ; while quite 
in the extreme north and in the Antarctic regions there are countries 
where the rivers of ice still descend into the sea, and stretch far into 
the gulfs. The glacier of the Bay of Magdalene, which Messrs. Martins 
and Bravais have explored, projects far into a fjord which is fifty-five 
fathoms deep; and the terminal cliff of ice, driven out by the weight of 
the upper snows, presents a curved line, turning its convexity toward the 
open sea. On still colder coasts, such as the north of Greenland, and at 
the South Pole, the outline of the Antarctic countries, even the bays are 
entirely filled up with ice, and this running into the sea gives a regular 
* See the chapter entitled Snow and Glaciers ; Oscar Peschel, Ausland, 1866. 



134 THE OCEAN. 

outline to the whole coast. The waves of the open sea dash against a 
long wall of crystal, and the icy layers disguise the true form of the ar- 
chitecture of the continents, as the fluvial alluvium and marine sand-banks 
do in other climates. Nevertheless, deep valleys, hidden by the ice-fields, 
are also cut into the line of these polar coasts too, and in a future geo- 
logical period, when the ice shall have disappeared, these incisions of the 
continent Avill become in their turn fjords, similar to those of Scandinavia. 

At the epoch when the bays of Scandinavia were filled with ice, as 
those of Northern Greenland are in our days, they preserved their primi- 
tive form, excepting that the lateral walls and the rocks at the|f)ottom 
were grooved and polished by the friction of the mass in movement and 
the fragments which it carried with it. The blocks of stone fallen on 
the snow and on the surface of the glacier, the heaps of pebbles and 
eai'th torn by storms and thaws from the sides of the mountain, formed 
moraines exactly similar to those which are now seen on the diminished 
glaciers of the Scandinavian mountains. But these moraines, instead of 
crumbling away with the ice, in some valleys thousands of feet above 
the sea, were carried to the very mouths of the fjords in the open sea, 
and plunged into the middle of the waves with the pieces detached from 
the glacier itself The successive debris of rocks and pebbles must nec- 
essarily gradually raise the frontal submarine moraine ; and, in fact, at 
the entrance of all the Scandinavian fjords heaps of deposit are found ris- 
ing like ramparts out of the deep water. The seamen of Norway give 
the name of " sea-gates " to these natural barricades, which serve as limit • 
to the ancient glaciers, and where the fish from the neighboring waters 
assemble in myriads. Ofi" the coasts of Western Scotland, as at the en- 
trance to the small gulfs of Finisterre, the ridges of submarine banks 
and reefs are observed, which are probably nothing else than ancient 
terminal glacial moraines. 

After the period which preceded the present era, the glaciers of Scandi- 
navia retreated little by little into the interior of the fjords, then ceased 
to touch the level of the sea, and their lower extremity mounted higher 
and higher in the open valleys on the sides of the mountains. It was 
then that the immense geological labor of filling up the bays commenced 
for the torrents and the sea. The fluvial waters brought their alluvium, 
and deposited it as an even strand at the foot of the mountains, while 
the sea leveled with sheets of sand or mud all the fragments of rocks 
which it had worn away by its waves. Already in a great number of 
Norwegian fjoi'ds this work of transforming the domain of the waters 
into firm land has made very sensible progress, and if we knew the 
amount per century of the augmentation to the shores, we should be able 
to calculate approximately the epoch at which the valley was free from 
ice. On the inclined eastern side, toward the open country of Sweden, 
an analogous work is accomplished; there the glaciers have been re- 
placed, not by the waves of the sea, but by the lacustrine waters divided 
into different basins, and these waters also retreat gradually before the 



The Ocean. <^c. 



FJORDS OF NORWAY. 



PL. V III. 



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VOAST-LJNES MODIFIED BY CLIMATE. 



185 



alluvium of the torrents. In the same way, in the great chain of the 
Swiss Alps, several deep depressions, formerly the beds of immense gla- 
ciers, have become a sort of continental fjord, such as the lakes of Mag- 
giore Iseo, Lugano, Como, and Garda.* These lacustrine basins are 
closed at the south by large moraines, like the sea-gates of Norway, and 
their waters, like those of the fjords, are gradually displaced by the al- 
luvium brought down by Alpine torrents. 




Fig. 52.— Ancient Fjords of Northern Italy. 

Situated more to the south than the fjords of Scandinavia, and nearer 
the source of the warm current flowing from the Antilles, the western 
bays of Scotland must have been free from ice long before the coasts of 
Norway, and it was still earlier that the indentations of the coast-lines 
of Ireland and Brittany ceased to serve as beds to the solidified snows 
of the surrounding mountains. As to the shores of the British Islands 
turned to the east toward the North Sea, they have certainly long been 
freed from ice, for then, as now, the winds from the west and south-west 
prevailed in Europe, and carried the rains over the slopes of the mount- 
ains inclined toward the Atlantic ; on the opposite slope the glaciers are 
sooner melted, because of the want of the necessary moisture. This is 
the reason of the striking contrast presented in the British Isles and Ice- 
* Oscar Peschel, Ausland, 1866. 



136 



THE OCEAN. 



land by the western coasts all cut into deep bays, and the eastern shores 
whose fjords are less deep, or even completely obliterated by alluvium. 
In the same way, at the south of America, the rains being much more 
abundant on the western slope of the mountains of Patagonia, the gla- 
ciers have descended much lower into the valleys, and the fjords, pre- 
served by the ice in their primitive state, make all this part of the Amer- 
ican coast-line a real labyrinth. The form of the continents themselves 
must be explained by the movements of the atmosphere. 




Fig. 53.— Fjords of the Sonth-east of Iceland. 

After the retreat of the glaciers, the work of rendering the shores reg- 
ular goes on in the various countries with more or less rapidity, accord- 
ing to the form of the continents, the depth of the fjords, and all the phe- 
nomena which constitute their geographical circumstances. In certain 
countries where the rivers are of little importance, as in the peninsulas 
of Denmark and in Mecklenburg, the fjords are first closed on the sea- 
ward side, and then become long and narrow lagunes, separated from the 
salt waves by the sandy beaches. Those gulfs, on the contrary, where 
great rivers discharge themselves, are gradually filled up by alluvium in 
those parts the farthest from the ocean, and are changed little by little 
into estuaries. Finally, many shores, ainong others those of eastern Ice- 
land, present a great number of fjords, one beside the other, which are 



FILLING UP OF FJORDS. 



137 



luxn-owcd at tlie same time above and below by the deposit from the sea, 
and that of the streams from the interior. It is thus tliat a multitude of 
ancient gulfs in Scandinavia, England, and France have been gradually 
changed into dry laud. The gulfs of Christiansand, in Norway, of Ca- 
rentan, in France, formerly projected in all directions from deep abysses, 
the place of which is occupied now by fields and marshes. 




^r& 



Fig. 54.— Filled-up Fjords of Christiansand. 

Whatever may be the diversity of means employed by nature in filling 
np the ancient glacial bays, the labor is accomplished in due time, and 
we may state that from the temperate to the equatorial zone the curves 
of the shore increase in regularity. The innumerable ports which pene- 
trate deep into the northern lands are succeeded in the south by more 
and more inhospitable maritime shores, because of destitute indentations. 
And on the coasts of the torrid zone, which are destitute of the mouths 
of rivers, vessels must sail along for hundreds of leagues before finding 
a harbor of refuge. It is the three southern continents, South America, 
Africa, and Australia, which present in their outline a most uniform de- 
velopment of coast and are most destitute of bays. 

If we can rightly consider each glacier as a natural thermometer, indi- 
cating by its advance and retreat all the changes of local temperature, 
we may in the same way regard the general character of the coasts, from 
the fjords of Greenland and Norway to the' long shores of Equatorial 
Africa, as a visible representation of the changes of temperature which 
have taken place on the surface of the globe since the glacial epoch. If 



138 



THE OCEAN. 




Pig. 55.— Ancient Fjords of Carentan. 



by long and patient study we succeed in measuring the time which is 
necessary for the alhivium of the sea and rivers thus to modify the forms 
of valleys once filled with ice, we can then estimate the amount of time 
which has elapsed since the glacial epoch. This vague period, which ac- 
cording to various geologists comprehends thousands or millions of years, 
will assume, at least for the times nearest to us, a more precise meaning, 
and will arrange itself like the centuries in the chronology of mankind. 



ENCROACHMENT OF THE SEA. 139 



CHAPTER XVin. 

DESTRUCTION OF CLIFFS.' — THE COASTS OF THE CHANNEL. THE STRAITS 

OP DOVER. ACTION OF SHINGLE AND SAND. GIANTS' CALDRONS. 

SPOUTING WELLS ON THE COASTS. — TIDAL WELLS. 

Although there is necessarily an equilibrium between the work of dem- 
olition and that of reconstruction, we would nevertheless, at first sight, 
be tempted to believe that the sea took the greatest pleasure in destruc- 
tion. On contemplating the cliffs, those perpendicular walls which on 
various coasts rise many hundreds of yards above the level of the sea, 
we are struck with awe to see how the repeated assaults of the waves 
have been sufiicient thus to cut the mountains and hills whose bases 
were formerly gently sloped to the water. From the top of these cliffs, 
we see the tumultuous ocean spread at their feet like a ^^lane surface, and 
we no longer distinguish the billows but by their reflections, or the ' 
breakers but by their garland of foam; the multiplied sound of the 
waves melts into one long murmur, which dies away and rises to die 
away again. And yet this water, which we see below at such a great 
depth, and which seems powerless against the solid rock, has thrown 
down piece by piege all that part of the hill or mountain, of which the 
cliff is but a gigantic memorial . then, after having thrown down these 
enormous masses, it has reduced them to sand, and perhaps caused the 
very trace of them to disappear. Often not even a rock remains where 
promontories once jutted out. The phenomena ascertained even during 
the short life of man are facts so grand in their progress, and so remark- 
able in their effects, that an English savant, Captain Saxby, has proposed 
to make of them a special science, Ondavorology.'^ 

To gain some idea of the destructive force exercised by the waves of 
the ocean, it is sufficient to contemplate them on a tempestuous day from 
the height of the chalky cliffs of Dieppe or Havre. At our feet we see 
the army of whitening billows rush to the assault of the rocks. Driven 
at the same time by the wind, the tide, and the lateral current, they leap 
over the rocks and shelves of the shore, and strike the base of the cliffs 
obliquely. Their shock causes the enormous walls to tremble to the veiy 
summit, and the roar reverberates in all their angles with an incessant 
thunder. Dashed into the fissures of the rock with terrible force, the 
water sweeps away all the clayey and chalky matter, and gradually M,ys 
bare the solid beds, wrenches large blocks out of them, I'olls them on the 
strand, and breaks them into shingle, which it drives along with a dread- 
ful noise. Through the eddy of boiling foam which besieges the shore, 
one can only now and then perceive the work of demolition ; bivt the 
* Nautical Magazine, January, 1864. 



140 



TH^ OCEAN. 




Fig. 56.— Eoads of tlie Downs. 

waves are so laden with fragments that they present a blackish or earthy 
color, as far as the eye can reach. 

When the storm has ceased, the encroachments of the sea can be meas- 
ured, and we can calculate the millions of cubic yards of stone ingulfed or 



ENCROACHMENT OF THE SEA. 141 

transformed into shingle and sand. Toward the end of the year 1862, 
during one of the most terrible tempests of the century, M. Lennier saw 
the sea batter down the rocks of La Ileve to a thickness of more than 
fifty feet. Since the year 1100, the waters of the Channel, aided by rain, 
frost, and other agents, that act strongly on the upper strata, have cut 
down this cliff by more than 1500 yards — that is to say, more than two 
yards per year. The spot where the village of Sainte Adresse formerly 
stood has given way before the flood, and is replaced by the bank of 
I'Eclat.* ]M. Bouniceau, one of those savants who have specially studied 
the phenomena of erosion of shores, estimates the fraction of cliff which 
is carried away by the sea on the coasts of Calvados at above a quarter 
of a yard on an average yearly, while on the coasts of Seine Inferieure 
the annual erosion may be considered as nearly a foot. 

In some places on the southera and eastern coasts of England, the in- 
vasions of the sea take place with an equal or even superior rapidity, for 
the farmers generally count on the loss of about a yard per year along 
the cliff.f To the east of the peninsula of Kent, the waters have ad- 
vanced more than three miles toward the west since the Roman period. 
In their successive invasions, they have subnlerged the vast domains of 
the Saxon Earl Goodwin, and have replaced them by the terrible Good- 
win Sands, where so many ships are lost every year; and they have 
transformed the narrow lagune of the Downs into great open roads. Ac- 
cording to the calculations of M. Marchal,J the total amount of denuda- 
tion which the waters of the eastern part of the Channel carry on every 
year is equal to above thirteen millions of cubic yards. 

The Straits of Dover are being continually enlarged by the action of 
atmospheric influences, the waves, and the current which flows from the 
Channel into the North Sea, The patient researches of M. Thome de 
Gamond, an engineer to whom we owe the fine project of the interna- 
tional tunnel between France and England, have proved that the cliff of 
Gris-Xez, the nearest point of the French coast to Great Britain, loses on 
an average more than twenty-seven yards per century. If in former ages 
the progress of erosion was not more rapid, it would be about 60,000 
years before the present epoch that the isthmus connecting England with 
the continent was broken by the pressure of the waves. Xevertheless, it 
is impossible to indicate any date, since at this place the ground has sunk 
and risen at various intervals: ancient beaches four or five yards above 
the present level of the sea, as well as submerged forests, testify to these 
successive oscillations.§ 

Along the coast of France, to the east of Cape Antifer,the pebbles re- 
sulting from the denudation of the cliffs are continually advancing to- 
ward the mouth of the Somme. Arrested at about six miles beyond these 

^ * Lamblardie, Bande, Revve des derix Mondes. 
" t Beete Jukes, School Manual of Geology, p. 90. 

\ Annales des Fonts et Chaussees, ler sem., p. 201. 

§ Day, Geological Magazine, 186G. 



142 



TEH OCEAN. 



last flinty cliffs, by the promontory of Hourdel, so named from the dash 
{heu7^t, Fr.) of the waves, they are subsequently taken up by the current 
which runs toward the strait. Ti-iturated more and more, they travel 
from sand-bank to sand-bank, and after having passed the strait, are de- 
posited in beds of mud either on the surface of the innumerable banks of 
the North Sea, or on the coasts of Flanders, Holland, and eastern En- 
gland, It is these deposits which are called by the expressive name of 
gain de flot (" winnings from the waves "), in the neighborhood of the 




G'-wAV'-ofParfe 




nil)] 




ki^^a^ 



_ w 



G^J5 W.of Pairis 



Fig. 57.— Map of Abervrac'h. 

Channel. The ten millions of cubic yards of fragments taken annually 
from the cliffs of- Sussex and Kent, as well as from those of Calvados and 
the Pays de Caux, are carried back to the coasts of the northern coun- 
tries, and it is at the expense of the shores of the Channel that the pol- 
ders of Holland and the Fens of Norfolk and Lincolnshire are formed. In 
consequence of this double work of erosion at one point and deposit on 
another, the shores situated to the north of the straits pr^ent a perfect 
contrast with the coasts of the Channel. While the cliffs of France and 
England, on the borders of this sea, are cut into concave bays, the beaches 



EROSION OF CLIFFS. 



143 



which stretch to the north of the Straits of Dover uniformly exhihit a 
convex arrangement. The waves give back in sand and mud what they 
have taken in rocks and boulders.* 

We must not think that it is the force alone of the breakers that de- 
molishes the cliffs along the shore. The sea Avould be almost powerless* 
against the hard rocks ■ if, on approaching the shore, it was not charged 
with all kinds of debris, blocks and pebbles, sand and shells — projectiles 
which are hurled by every wave against the cliffs which oppose them. 







Fig. 58.—" Giants' Caldrons " of Haelstolmen. 



Using thus the stones that have fallen as so many battering-rams, the 
billows roll them over the strand to the foot of the cliffs, dash them 
against the projecting points, and finally break off masses and reduce 
them to sand. The sand itself, incessantly washed against the rocks, 
weai'i away the most solid layers little by little, and thus continues the 
work of destruction commenced by the shingle : it is in great part the 
fragments of the promontory itself which serve to further its destruc- 
tion. On all the rocky coasts of Scandinavia, Scotland, Ireland, and Brit- 
tany, the multitude of reefs that extend seaward for a great distance 
from the shore are nothing else than the ancient foundations of the conti- 
nent, which have been gradually razed by denudation to a level with the 




Fig. 59.— Section of the "Giants' Caldrons," of Haelstolmen, taken aloug the line a b, in Fig. 58. 



water. From the top of any hill on the coasts of Paimpol, Morlaix, and 
Abervrac'h, we may thus distinguish at low tide what was the primitive 
form of the shore. 

■" Marchal, AnnaJes des Fonts et Chause'es, ler sem., p. 204. 



144 THE OCEAK 

The deep and regular excavations known under the name of "Giants' 
Caldrons " are the most curious of the geological feats accomplished by 
the scattered blocks. Every stone reposing on a ledge of the rock where 
the waves break hollows out during the course of ages a kind of well, 
the walls of which are polished, and planed by the friction. Finally, 
these cavities, where the gradually rounded stone does not cease to oscil- 
late, acquire a depth and width of several yards, and these are then, ac- 
cording to tradition, the caldrons where the giants prepared their repasts 
in former times. Very remarkable excavations of this kind exist on the 
coasts of Scandinavia, where blocks of granite, rolled along by a furious 
sea, are retained by abrupt rocks in a great number of cavities. 

A phenomenon not less interesting than the revolving of the stones in 
the giants' caldrons is the sudden a|)pearance of columns of sea-water, 
which spring in jets through the fissures of the rock. When a large 
wave is swallowed up in one of the fissured caverns on the coast, its force 
is sometimes so great that the rock resounds as with the discharge of 
artillery. The mass of water drives the air before it, and, not finding in 
the" walls that surround and compress it a large enough space to develop 
itself, springs through the crevices of the vault. Most of these fissures, 
gradually sculptured anew by the waters which escape from th%m, at 
length assume the appearance of real wells, where each return of the 
wave is signalized by a sort of geyser of variable dimensions. There 
are some which spring several yards high, and can be seen at a great dis- 
tance, like the jet of water by which the whale betrays himself afar off; 
hence arises the name of blowers {souffleurs) given in many countries by 
sailors to these phenomena on the shore. 



Fig. CO.— Tidal Wells. 

The pressure of .the tide does not make itself less felt than the force of 
the waves in the interior of the fissured rocks of the coast. It does not, 
it is true, cause magnificent fountains to spring far above the sea, but it 
lowers the level of the water in all the wells near enough to the shore; 
even in those that are filled with fresh water. And this is what theory 
could have indicated beforehand ; the mass of water that penetrates far 
into the crevices of the rock retains the waters which infiltrate from the 
interior; the latter, salt or fresh, remain in their reservoirs, and rise at the 
same time as the tide ; then, when the ebb commences, they flow into the 



MARINE GROTTOES. I45 

sea, find overflow again as soon as the pressure of the ^sing water ceases. 
Where the rocks of the coast are much fissured, which is ahiiost every- 
where the case with cliffs composed of calcareous strata, there exist these 
"tidal" wells, which rise and fall alternately with the tide. We may 
specially cite those of Finland, near Wasa, those in the environs of Roy- 
an, on the right bank of the Gironde, and, above all, those of the Bahama 
Islands. In many of these islands, all the wells, without exception, are 
I'egulated by the flow of the sea,* 

There are even certain coasts opening so deeply into large hollows, on 
the side toward the sea, that the waves penetrate to a great distance into 
the interior of the continent. A curious example of this is seen in that 
part of Louisiana known under the name of the Attakapas. There the 
prairies of the coast, protected against the tempests of the Gulf of Mexico 
by chains of sand-banks and long islands parallel to the shore, incessantly 
gain upon the ocean. But they are only solid on the surface, for their 
roots are bathed by the sea-water, which advances far into a bay with 
invisible outlines. The fishermen do not fear to venture on these float- 
ing meadows, resembling fens in every respect, and it is by piercing the 
ground xinderneath their feet that they procure the fish hidden in these 
retreats. 

Nevertheless, such floating shores can only exist on a small number of 
coasts, where the physical circumstances are quite exceptional ; usually 
it is by grottoes and caverns hollowed out of the solid rock that the wa- 
ters of the ocean penetrate fa^j into the land. It is not to be doubted 
that there are below the level of* the sea multitudes of those rocky gal 
leries, but only those are known that are open to the strike of the waves, 
like the azure grotto of Capri. Lower down, the water closes the en- 
trance to the lateral caverns, which will doubtless long remain unknown 
to us. But if we can not explore grottoes still filled by the sea, we 
can at least see on elevated coasts like those of Scandinavia immense 
caverns which the waves once freely traversed. One of the most impos- 
ing grottoes in the whole world is that which penetrates the splendid 
rock of Torghatten, rising like an enormous pyramid to more than 900 
feet, on an island of Northern Norway. This gallery, through which sea- 
men see the light glimmering, is of an astonishing regularity. The 
thresholds of the immense jDortals, one of which has an arch of nearly 234 
feet, and the other of nearly 144 feet span, are found on each side to htve 
the same elevation of 375 feet above the level of the sea. The ground, 
covered with fine sand, is almost level, and formed like the floor of a 
tunnel, where carriages might roll. The lateral walls present almost 
throughout a polished surface, as if they had been cut by the hand of 
man, and rise vertically to the spring of the arch ; only toward the cen- 
tre of the grotto the vault is less elevated than at the two extremities. 
Seen through this gigantic telescope, 900 feet long, the promontories, 
islets, innumerable reefs, and the thousand white crests of the breakers, 
* R. Thomassy, Bulletin de la Societe de Geographie, 18G4. 
10 



146 THE OCEAN. 

form a spectacle ^f incomparable beauty, especially when the sun illu- 
mines the whole landscape with its rays.* 

When the waves of the sea can not enter into the caverns remote from 
the shore except by narrow channels, it often happens that a rivulet of 
salt water regularly flows toward the interior of the land, without ever 
returning to the ocean. This strange fact, which may seem at first sight 
a reversal of the laws of nature, may be observed on various points on 
the coast of calcareous countries, and especially on the coasts of Greece 
and the neighboring islands. 

Near Argostoli, a commercial town in the island of Cephalonia, four 
little torrents of sea-water, rolling on an average fifty-five gallons of 
water per second, penetrate into the fissures of the clifis, flow rapidly 
among the blocks that are scattered over the rocky bed, and gradually 
disappear in the crevices of the soil. Two of these water-courses are 
sufiiciently powerful to turn throughout the year the wheels of two mills 
constructed by an enterprising Englishman. Though the subterranean 
cavities of Argostoli are in constant communication with the sea, and the 
entrance to the canals is carefully freed from the sea-weed that could ob- 
struct the passage, or at least retard the current, the waters are not the 
same height in the grottoes as in the neighboring gulf. This is because 
the calcareous rocks of Cephalonia, dried on the surface by the sea-breeze 
and the heat of the sun, are pierced and cracked throughout by innu- 
merable crevices, which are so many flues aiding the circulation of the 
air, and the evaporization of the hidden oaoisture. We can compare the 
entire mass of the hill& of Argostoli, -with all their caverns, to an im- 
mense Alcaraza, the contents of which are gradually evaporated through 
the porous clay. In consequence of this constant loss of liquid, the level 
of the water is always lower in the caverns than in the sea, and to restore 
the equilibrium, the brooklets, which are fed by the waves, descend in- 
cessantly by all the fissures toward the subterranean reservoirs. It is 
probable that the constant evaporation of the salt water has resulted in 
the accumulation in the cavities of the island of enormous saline masses. 
Professor Ansted has calculated that the discharge of the two great ma- 
rine streams* of Argostoli would be sufiicient to form each year a block 
of more than 1800 cubic yards of salt.f 

* Vibe, Kiisten und Meer Norwegens., Mittheilungen von Petermann, 1860. 
t The Ionian Islands in the year 1863. 



UNDEMMINING OF ROCKS. 147 



CHAPTER XIX, 

UNDERMININfi OP ROCKS. VARIED ASPECT OP CLIPPS. PLATPORMS AT 

THEIR BASES. RESISTANCE OP THE COASTS. BREAKWATERS PORMED 

BY THE RUBBISH. HELIGOLAND. DESTRUCTION OP LOW SHORES. 

All the rocky promontories exposed to the violence of storms, or sim- 
ply washed by a current, are undermined at their base. The wearing 
away is accomplished in a more or less rapid manner, according to the 
progress of the waves, the distribution and inclination of the strata, the 
hardness of the rocks, and their chemical composition. The method of 
destruction depends, at the same time, on various hydrological and geo- 
logical conditions. Strange as this assertion may appear, the water of 
the sea can even in certain cases destroy the rocks on its borders by 
combustion. Thus, the cliffs of Ballybunion, on the western coast of Ire- 
land, long presented the appearance of a rampart of smoking lava. 
Those rocks which the waves of the Atlantic have pierced with grottoes, 
and sculptured in massive and fantastic forms, having one day fallen 
down very extensively, the alum and iron pyrites, which is contained 
in considerable proportion in the rocks, were exposed to the action of 
the atmosphere and the sea-water. A rapid oxydation took place, and 
produced a heat sufficiently intense to set the whole cliff on fire. For 
weeks the rocks were burning like a vast coal fire, and masses of vapor 
and smoke rose like clouds above the high wall besieged by the surf 
Scattered around the space where the fire had prevailed, a heap of melt- 
ed scoriae, and clay transformed into brick by the violence of the fire, 
was to be seen. 

Since such is the diversity of destructive agents employed by nature, 
that, as we can easily understand, the aspect and form of the rocky coasts 
varies likewise in a remarkable manner. Thus the cliffs of England and 
Normandy, which are composed of somewhat friable rocks, fall when 
their lower strata are eaten away, and their sides being occasionally in- 
terrupted by " valleuses " (narrow openings where temi^orary or perma- 
nent brooks flow), they resemble enormous walls from 150 to 300 feet 
high. In the islands of the Baltic Sea, the chalky rocks, less exposed 
to the fury of the tempests than those of Western Europe, are also less 
abrupt, and forests of beech-trees descend like sheets of verdure over the 
ruins of the cliffs. Elsewhere, especially on the coasts of Liguria, the 
promontories, formed of limestone rocks harder than chalk, do not fall in 
when their lower strata are carried away by the sea, and the waves, in- 
cessantly excavating the bases of these rocks, may carve them into colon- 
nades, arched gate-ways, winding galleries, and vast grottoes, where the 
trembling water lights up the vaults with its azure hues. Other cliffs, of 



148 THE OCEAN. 

which the promontory of Socoa, near StJ^^an de Luz, may be considered 
as a type, are composed of slate rocks, variously inclined toward the sea. 
Worn away by the waves, some of the layers of schist are detached, oth- 
ers bend and part from each other, like the pages of an open book, allow- 
ing the water to glide in long, foaming sheets into the very heart of the 
cliff, to spring up again from it in immense spouts. Finally, on other 
coasts the rocks cut by vertical fractures are gradually isolated from one 
another, and separated into distinct groups by the action of the waters. 
Surrounded by a roaring sea, they rise on their rocky bases like towers, 
monstrous obelisks, gigantic arcades, or crumbling bridges. Such are the 
innumerable rocks which tower above the waves in the archipelago of the 
Orkney and Shetland islands. Black, slender, and enveloped with spray 
as with smoke, these wrecks of ancient cliffs justify the name of " chim- 
ney-rocks," which the English have given to many of them. On the 
northern coasts of Norway, not far from the polar circle, a rock rises in 
the midst of the waves, more than 900 feet high, which resembles a giant 
cavalier; hence its name of Hestmanden. 

We see that the rocks which the sea-wave has eaten away are very 
various in form. Still, we may say, as a general rule, that the inequali- 
ties of cliffs are in direct proportion to the hardness of the strata. The 
grooves that the waves slowly hollow out in the surface of the rock, the 
cavities that they scoop out in it, the arcades and grottoes which they 
excavate there, are the deeper the harder the stone is, for the beds of less 
solid formation fall in as soon as the lower layers are eroded. That part 
of the cliff which is only wetted by the foam and the mist of minute 
drops is less cut up than the base, and the grooves are less numerous 
there ; but no vegetation as yet appears. Higher up a few lichens give 
a tint of greenish gray to the stone. Finally, those bushes which delight 
in breathing the salt air of the sea make their appearance in the angles 
and on the cornices of the rocks. It is at 100 or 120 feet high that this 
vegetation begins to show itself on the cliffs at the border of the Medi- 
terranean.* 




Fig. 61.— Cliflf on the Mediterranean. 



Notwithstanding the astonishing variety of aspect presented by cliff's 
composed of various substances — chalk, marble, granite, or porphyry — 
we can still observe one trait of singular resemblance in the form of the 

* Boblaye et Virlet. G. CoUegno, Geologia dell' Italia. 



FORMATION OF CLIFFS WITH PLATFORMS. I49 

rocks which are covered by the' waters of the sea at the foot of the ab- 
rupt walls. This feature consists in the existence of one or two plat- 
forms of varying dimensions, situated at the base of the escarpments. 







FiK- 62.— Oceap Cliflf. 

On the coasts of the Mediterranean and other seas with a very slight 
tide, where the level of the waters hardly varies excepting under the in- 
fluence of the winds and storms, there is but a single one of these plat- 
forms ; while on the shores of the ocean, where the tides attain a height 
of at least several yards, two steps, one above the other, extend below 
the wall of the cliffs. When the rock is very hard the platforms present 
but a few yards in width, and perhaps may then be compared to a nar- 
row cornice, suspended at midway between two abrupt walls — that of the 
cliff, and that which plunges into the abyss of the water. On the other 
hand, when the rocks are easily cut, the terrace of one or several stages 
over which the waves roll has sometimes many hundreds of yards in width. 




^^1 

Fig. 63 — Tides of Inishmore. (Kinahan.) 
a. Deposit of tempests. h. Terrace of equinoctial tides. c. Terrace of ordinary high tides. 

dd. Intermediary terraces, e. Terrace of ordinary low tides. /. Low equinoctial tides. 

At Inishmore, on the western coast of Ireland, the cliff j^resents a succes- 
sion of regular steps like those of a staircase cut out for giants. The 
highest step, all incumbered with blocks, is that attained by the waves 
during a tempest ; lower down are those bathed by the spring-tides, and 
then that where the ordinary tides are arrested. Still lower are the inter- 
mediary terraces, and the last two steps of the staircase are those where the 
water breaks during ordinary ebb, and at the low tides of the equinoxes.* 
* Kinahan, Geological Magazine, August, 1866. 



150 THE ocean: 

* 

It will be easily understood that thes^ submarine ledges were formerly- 
embedded in the thickness of the rock; they have resisted the assault of 
the waves, while the higher strata, sapped at their base more or less slow- 
ly, have fallen into the water. As the force of the waves is felt much less 
in the mass of waters than on the surface of the sea, the rock only allows 
itself to be cut into at the place where the breakers dash. But its sub- 
merged slopes remain relatively intact, and maintain more or less exactly 
• the ancient outline of the coast. This is the reason why there exists on 
the shores of the Atlantic and other seas, the level of which oscillates 
alternately with the ebb and flow, two platforms, one above the other, 
which correspond, the one with the level of low water, the other with 
that of high water. At the time of flow, the waves, urged by the tides, 
and more often too by the wind which accompanies the tide,* dash im- 
petuously against the rocky walls, and push on vigorously their labors of 
destruction. During the period of the ebb, on the contrary, the water 
which breaks on the shore is retained by the current of low water, and is 
as though attracted toward the open sea : neither does it attack the clifi" 
with as much energy as the rising tide. The difierence which exists be- 
tween the force of the waves of the flow and those of the ebb can be 
measured by the respective extent of the intermediary platforms. 

If the waves march constantly to the assault of the shore to transform 
into clifis the heights of the coast, the latter, on their side, are not satis- 
fied with merely resisting by their mass, and by the greater or less hard- 
ness of their strata, but many of them besides take care, one might say, 
to protect their threatened base against the waves. A thick vegetation 
of sea-weed, like floating hair, drapes the cornices, breaks the force of the 
surf, and changes into torrents of eddying foam the enormous rollers 
which rush to attack the rocks with great speed. Besides, all that por- 
tion of the rocks comprised between the levels of high and low water is 
covered with balani and other shells, numerous enough to give the stone 
the appearance at certain hours of a swarming mass, and to form it after- 
ward into an immense immovable carapace. f ' 

The coasts thus protected are precisely those which, by the solidity of 
their rocks, would best resist the attacks of the sea. As to the cliffs, 
composed throughout their thickness, or only at their base of less resist- 
ing materials, they gave way too often for the mollusks and sea-weed to 
venture in great numbers on that part of the rock which the waves have 
just assailed. Great blocks detach themselves from the upper strata, 
and fall on the beach. Afterward, under the action of the waves, they 
break into smaller pieces, then into pebbles, which the surge rolls and 
chafes incessantly. Under these fragments, constantly moved by the 
wave, no germ of animal or plant can develop itself, no living organism 
brought from the open sea can exist there. A desert is made even in 
the waters which dash against the roaring mass. 

* See the section entitjed The Air and the Winds. 

t See the sections entitled The Earth and its Flora, and The Earth and its Fauna. 



NATURAL BREAKWATERS. 151 

When this is the case, it is the crumbling masses and the pebbles of the 
strand which themselves serve ao bulwarks of defense to protect the wall 
of the cliffs from fresh damage. Supported in a slope on the lower part 
of the rock, or else scattered in the waves and transformed into shelves, 
the iixllen blocks break the force of the waves, and retard the progress 
of erosion. It is thus that on the coasts, of the Mediterranean, near 
Vintimillia, the lower strata of the cliffs are composed of a sandy clay, 
which the rain alone suffices to wash away, and this gives rise to a talus 
of masses of solid conglomerate detached from the upper layers, which 
thus protects the cliffs from the fury of the waves. In the same way, on 
the sterile shores of Brittany, the blocks of granite, cracked in all direc- 
tions, and converted into shingle which the sea carries away and returns 
again, maintain intact during centuries the walls of rocks of which they 
formerly made a part. 

The cliffs of Normandy, composed of materials much less hard than 
those of the promontories of Brittany, are also more easily worn away ; 
still, we must attribute their rapid erosion principally to the coastal cur- 
rent which carries away the shingle accumulated at the base of the rocks. 
The talus of fallen blocks constitutes at first a perfectly sufficient defense 
against the fury of the waves ; but little by little the chalky part of the 
rock is dissolved and deposited here and there on the mud-banks, while 
the masses of flint disengaged from the substance of the stone cease to 
present a sufficient resistance to the waves, and are carried away into the 
neighboring bays in immense processions parallel to the shore. On the 
south coast of England the current of the coast is much less energetic, 
and the talus can, in consequence, long resist the attacks of the sea. A 
few years ago the waters undermined with a threatening rapidjty the 
base of the cliff which rises not far from Dover, on the western side, and 
which the English have consecrated to Shakspeare, in remembrance of 
the beautiful description which he has given of it in King Lear. To 
preserve this historical promontory, the houses that it supports, and the 
railroad which runs through it in a tunnel, they formed the plan of blow- 
ing down the upper part. In the presence of an immense crowd, assem- 
bled to see this new spectacle, they fired hundreds of pounds of powder 
buried in a mine, and enormous masses of rock fell with a crash from the 
top of the hill ; and now the force of the waves is broken on their talus. 
Mr. Beete Jukes thinks that during eighteen centuries this cliff and the 
neighboring rocks have been worn away by nearly one mile.* 

In the North Sea there is an island which, by a singular misapprehen- 
sion, was believed to have been consecrated to Freya, the goddess of Love 
and Liberty, and whose ancient name of Halligland (land with the inun- 
dated banks) has been transformed for foreigners into that of Heligoland 
(Holy Land). The island, composed entirely of mottled stone, formerly 
surrounded by cretaceous beds, presents to the sea all round a cliff about 
200 feet high, worn away at the base by the waves. By employing the 
* School Manual of Geology, p. 89. 



152 



THE OCEAIS'. 



heroic means which the English engineers; have applied to the defense of 
Shakspeare's Cliff, and which the garrison of Heligoland had also inaugu- 
rated in the year 1808, by bombarding a crumbling cliff,* the inhabitants 
might surround their island with a great circular breakwater. But this 
dike would not last long, for the strata of mottled stone do not contain 




64.— Heligoland. 



those beds of pebbles which serve to form shingle for a beach. All the 
blocks would soon be dissolved by the waves, and not a single fragment 
remaining to protect the lower strata of the cliff against the destructive 
action of the waves, the work of erosion would freely resume its course. 
* Hallier, Nord-See Studien, p. 73, 



INUNDATIONS OF TEE COASTS. 153 

Devoted to certain destruction, the island is gradually melting in the 
waters, like an immense crystal of salt. 

The learned do not all give the same degree of confidence to the docu- 
ments relative to the ancient extent of Heligoland. Some, such as Wie- 
bel,* regard those testimonies of the past as if destitute of sufficient au- 
thenticity, and think that the lessening of tlie island is accomplished very 
slowly. Others, on the contrary ,f more respectful to the affirmations of 
the chroniclers, believe that in the space of five centuries the island has 
diminished by at least three-quarters. However it may be, it is cerflfcin 
that the partially inundated lands, to which the island owes its name, 
have long since ceased to exist. It is equally certain that, toward the 
end of the seventeenth century, an isthmus still^nited Heligoland to an- 
other islet, the cliffs of Avhich rose to about 100 feet in height, like the 
principal island : two excellent ports, which gave the island a great stra- 
tegical importance, opened to the north and south between the two rocky 
masses and their submarine extensions. The eastern island has now dis- 
appeared, and its cliffs are replaced by a few dunes and sand-banks, un- 
covered at low water : the ports no longer exist, and the ships of war 
drawing most water can sail freely where the isthmus still existed less 
than a century and a half ago. Who would now recognize in this rock 
of Heligoland, hardly a mile and a half long, and about 2000 feet broad, 
the land of which Adam de Bremse speaks in 1072, and which was then 
" very fertile, rich in corals, in animals, and birds," and which extended, 
says Karl Miiller, " over a space of 900 square kil0metres."J In the pres- 
.ent day, a few rows of potatoes and a few meagre pastures are the only 
remains that testify to the ancient fertility of Heligoland. 

If the sea thus destroys countries bordered all round with rocky prom- 
ontories, it respects still less the low strands which, in consequence of 
some modifications in the geography of the coasts, or in the relief of the 
submarine banks, are situated across the currents. In the very front of 
Heligoland, the shores of Hanover, Friesland, and Holland, which former- 
ly seemed to sink gradually,§ offer the most striking example of this de- 
structive power of the sea. During sixteen hundred years — that is to 
say, ever since written history commenced in these countries — the life of 
the inhabitants of the shores has been nothing but an incessant strife 
against the encroachment of the waters. During this period the great 
irruptions of the sea may be counted by hundreds, and among these 
there are some which, according to the chronicles, must have drowned 
whole populations of fifty and a hundred thousand souls. During the 
course of the third century, tradition tells us that the island of Walche- 
ren was separated from the continent; in 860 the Rhine rose, inundating 
the country ; the palace of Caligula {arx Brita7i7iica) remaining in the 

* Die Insel Helgoland. 

t Von Maack, Z^itschrift fur die algemeine Erdkunde, 1860. 

X Die Gefahren der schleswigschen West kuste: Natur, March, 18G7. 

§ See the section entitled The Slow Oscillations of the Terrestrial Soil. 



154 



THE OCEAN. 



midst of the waves. Toward the middle of the twelfth century the sea 
made a new irruption, and the lake Flevo was changed into a gulf, which 
was still more enlarged in 1225, forming the Zuyder Zee, that vast laby- 
rinth of sand-banks, which, from a geological point of view, is still a de- 
pendency of the continent, and is separated by a long row of islands and 
dunes from the domain of the ocean. In the first years of the thirteenth 
century the Gulf of Jahde was opened at the expense of the land, and 
never ceased to enlarge itself during two hundred years. In 1230 the 
tewible inundation of Friesland took place, which is said to have cost 
the life of a hundred thousand men. The following year the lakes of 
Haarlem overflowed the ground, then, gradually increasing, united with 
each other to expand injp) an inland sea toward the middle of the seven- 
teenth century. In 1277 the gulf of the Dollart, which is nearly twenty- 
two miles long and seven miles wide, began to be hollowed out at the 
expense of the fertile and populous countries, and transformed Friesland 
into a peninsula. It was only in 1537 that they could arrest the inva- 
sions of the sea, which had devoured the town of Torum and fifty vil- 
lages. Ten years after the first invasion of the waters in the Dollart, 
an overflowing of the Zuyder Zee drowned 80,000 persons, and changed 
the configuration of the Dutch coast-line. In 1421, seventy-two villages 
were submerged at once, and the sea, on retiring, left only an archipelago 
of marshy islands and islets, covered with reeds and banks of mud, in the 
place of fields and groups of habitations: this is the country known un- 
der the name of Biesbosch (forest of reeds). Since this epoch many other 
hardly less terrible catastrophes have taken place on the coasts of Hoi-; 
land, Friesland, Schleswig, and Jutland.* 




• iig. 06.— Isle of Borkum in 173a. 

Of the row of twenty-three islands, which extended along the shore 
fifteen centuries ago, only sixteen fragments remain, and many are noth- 
ing else than simple ridges, of sand. The Island of Borkum, as is shown 
by maps with less than a century's interval, has been singularly lessened ; 
the Island of Wangerooge, the wreck of the antique country of Wanger- 
land, which was once united to the continent, and extended far into the 
sea, was in 1840 still a flouinshing and populous island, and during the 
* Von HofF; Von Maack ; Beyer ; Baudissin ; Karl Miiller, ete. 



ITieOceau.Ar DEPTHS OF THE ZUIDER-ZEE. 



PL. LV. 



3°£«Bt of Pax i 



<s. 



o ^ 



TerSrliellmtf [ 



^ 



Mieland 




:-^if Am eland I. :^T'^^'f-M 















/^Texel.i' "SV*^"*"--- ,. -^; v,V 



».«^^ 



*jjkieifel<ler f^^ 



•rettea 



^AltnUBBr 



Hoc 




Ss^rle 



t'-xv^'Vi^d.en 



Hcei'ftiiveeja 



Kanipea 'V i^i 









EDgraved byBiluircl. 



Drawa bv E.G'iilliauiu 



y . . . . 4 . . 



JfUas 



Jf 



INUNDATIONS OF THE COASTS. 



155 




Fie;. 60.— Isle of Borkum in 1S25. 



summer the bathers visited it in crowds. Now it is a strand of mud al- 
most entirely abandoned. The Island of Nordstrand has diminished by 
eleven-twelfths since the commencement of the seventeenth century, and 
of the twenty-four islets which surrounded it 300 years ago, there only 
remain eleven : the lead, when thrown out at the spot which was former- 
ly in the centre of the island, indicates a depth of seven fathoms. The 
Island of Sylt, and other lands of the coast of Schleswig, have been also 
much worn aw^ay, and it is known that in 1825 the sea opened a way 
quite across the peninsula of Jutland by hollowing out the Strait of Lym- 
fjord.* 

* Miiller, Gefahren der schleswigschen Westkiisie : Natur, March. 1867. 



156 . THE OCEAN. 



CHAPTER XX. 

NORMAL POEM OF SHOEES. — CUEVES OF " GEEATEST STABILITY." — POEMA- 
TION OP NEW SHOEES. — COAST EIDGES AND SAND-BANKS. — INLAND BATS. 

The shores most violently attacked by the sea are generally those 
which present the most indentations and promontories. The waves 
break most of all against the advanced cajDes that jut out farthest into 
the domain of the waters ; but in proportion as the points retreat before 
the tide which wears them away, the destructive power of the waves di- 
minishes ; its force will even, in time, be reduced to nothing when the 
base of the cliffs is sufficiently eroded, and describes no more than a 
slight curve in front of the coast. In fact, the outline of the coast which 
offers the greatest resistance to the assaults of the sea is not a straight 
line, as one might supjDOse, but a series of regular and rhythmical 
curves.* The waves do not cease to labor at remodeling the shore as 
long as the latter does not present a succession of creeks gently curved 
from promontory to promontory. Each one of these rounded bays re- 
produces in large the form of the wave which breaks on it, drawing on 
the sand of the beach a long elliptical curve of foam-flakes. 

The coasts of mountainous countries, to which the sea has already giv- 
en the desired contours, unite an extreme grace with an admirable maj- 
esty. Such are the coasts of Provence, of Liguria, of Greece, of the great- 
er part of the Iberian and Italian peninsulas. There every promontory, 
the remains of an ancient chain of hills razed by the waves, lifts its ter- 
mina,l point in a high cliff; each valley which descends toward the sea 
terminates in a beach of fine sand, with a perfectly regular curve. Ab- 
rupt rocks and gently sloping beaches alternate thus in a harmonious 
manner, while the various geological formations, the greater or less width 
of the valleys, the towns scattered on the heights or on the low shores, 
the curvatui'es of the coast, and the incessantly changing aspects of the 
water, introduce variety into the whole landscape. • 

Sandy shores, as well as rocky coasts, have a normal profile composed 
of a series of bays and points. But these points, the relief of which is 
modified by every wave, are generally more rounded in their extremity 
than the promontories of rock. The monotonous coast of the Landes, 
which extends over a length of nearly 140 miles, from the mouth of the 
Gironde to that of the Adour, may be taken as a type of the shores 
which the waves of the sea model at their will. On these coasts the uni- 
formity of the landscape is complete. The traveler in vain hastens for- 
ward ; he might believe he had hardly changed his place, so immutable 
does the aspect of the scenery remain ; always the same dunes, the same 
* Elie de Beaumont, Baude, etc. 



CURVES OF GREATEST STABILITY. 



\o\ 



shells scattered on the sand, the same birds assembled by thousands on 
the edge of the lagunes, the same lines of waves which pursue one an- 
other, and break with great noise in a sheet of foam. In the whole field 
of view the only remarkable objects are the spars of shipwrecked vessels 
that can be seen from afar on the white sand. However, the shores 
which present the most regular series of convex and concave curves. 




C7.— Curves of the Coast between Oneglia aocl Savone. 



which one might call the outline of the greatest stability, are exposed 
also to rapid erosions when the bulwark of defense which flanks them 
at either of their extremities yields to the pressure of the waves. Thus 
the shores of Medoc, which are the continuations of the uniform coast 
of Saintonge, to the south of the bay of the Gironde, have incessantly re- 
treated before the sea ever since the rocky promontory (of which the 



158 THE OCEAN. 

ledge of Cordouan is the sole remains) disappeared under the united rav- 
ages of the river and the ocean. 

But if the sea demolishes on one side, it builds up on the other, and the 
destruction of the ancient shores is compensated for by the creation of 
new coasts. The clays and limestones torn from the promontories, the 
shingle of every kind which is alternately thrown up on the shore and 
swept back in the waves, the heaps of shells, the silicious and calcareous 
sands formed by the disintegration of all these fragments, are the materi- 
als employed by the sea for the construction of its embankment, and the 
silting up of its gulfs. 

It is on «ach side of the cliffs or low points worn away by the waves 
that the work of reparation commences. Each wave accomplishes a 
double work, for in sapping the base of the promontory it loads itself 
- with fragments which it deposits immediately on the neighboring strand; 
by the same action it causes the point to retreat, and the shoi'e of the 
bay to gain. Thus, owing to two series of apparently contrary results — 
the razing of the j)oints and the filling up of the bays — coasts more or 
less deeply indented gradually acquire the normal form with gracefully 
rounded curves. Whatever be the outline of the primitive coast, each 
inflection of the new shore rounds itself like the arc of a circle from 
promontory to promontory. In those places where the ancient coast was 
itself semi-circular, the sand or gravel cast up by the billows is deposited 
on the beach; but when the coasts ai'e irregular and indented by deep 
creeks, the sea simply leaves them and constructs sands or shingle banks 
in front of them, which end by becoming the true shore. 

The formation of such a breakwater may be explained in a very simple 
manner. The waves of the open sea, driven against the shore, first strike 
the two capes placed as guardians at the two extremities of the bay; 
hei'e they break their force, and are thrown back against the tranquil wa- 
ters of the bay. Thus arrested in their speed, they deposit the earthy 
matters which they hold in suspension, and also the heavier fragments 
torn from the neighboring promontories. At the entrance to the fjords of 
Scandinavia, of Terra del Fuego, and all the other mountainous countries 
' with deeply indented shores, the clear and deep water of the open sea only 
brings with it a relatively small quantity of debris, and can only form a 
submarine bank* from point to point. But along the lower coasts, where 
the tide drives before it masses of sand and clay, the ramparts of allu- 
vium constructed by the waves emerge gradually from the bosom of the 
waters. 

Under the alternate influence of the ebb and flow, the sand and shingle 
are gradually deposited against the rocks of the capes, and thus they 
form at the entrance of the bay true jetties, the free extremities of which 
advance to meet each other. Being elongated unceasingly, the two seg- 
ments end by uniting midway between the two caj)es, and thus form a 
large arc of a circle, the convexity of which is turned toward the ancient 

* Darwin, South America, p. 24. 



FORMATION OF BANKS AND DUNES. I59 

shore. The most furious assaults of the sea only serve to consolidate 
these banks by bringing other materials to them, and raising them above 
the level of the tides. 

All these sea-banks present a geometrical regularity ia their section ; 
their form is, so to say, the visible expression of the laws which govern 
the undulation of the waves. Most often that part which fronts the sea 
is composed of several separate slopes which correspond to the different 
levels of low water, high tide, and storms ; but all Ihese beaches present 
uniformly a graceful curve, modeled by the breakers. At the base of 
the embankment the slope is very slight, and simply continues the de- 
clivity from the bottom of the sea; but it rises suddenly at an angle 
that is sometimes not less than from thirty to thirty-five degrees. Im- 
mediately beyond this edge a counter-slope begins, where the upper curve 
of every high wave spreads in a foaming sheet. Farther on rises a sec- 
ond talus, which the stormy waves sometimes strike and consolidate. 
The inclination of this second stage, which looks toward the sea, is very 
slight. From this side the materials of the embankment, sheltered from 
the force of the wind and from the violence of the waves, are gradually 
heaped up, and ruay even at length be covered by a bed of vegetable 
earth. Above this level dunes rise, or else we find the surface of the an- 
cient bay transformed into a lagune. This outline of the shores is repre- 
sented by the accompanying illustration, where the heights are strongly 
exao-o-erated. 






• Fig. 68.— Section of Sea-shore. 

Notwithstanding the looseness of the materials which compose them, 
the banks are more solid than the promontories of rocks against which 
they rest, and when the clifis have been leveled by the waves the banks 
of sand again extend from one ledge to the other. They can be displaced 
by the influence of the currents and the winds, but they do not the less 
continue apparently immovable and more durable than the mountains. 
They do not, however, present a continuous development. When the in- 
land bay is fed by one or several rivers, the mass of water which is dis- 
charged in this closed basin must necessarily break a passage to the sea, 
and pierce this ridge at the spot where it offei-s least resistance — that is 
to say, most often at one of its extremities. A remarkable example of 
this phenomenon is to be seen in Corsica, at the mouth of the Liamone. 
In covyitries where the year comprises a dry period and a rainy season. 



160 



THE OCEAN. 




Fig. 69.— Mouth of the Liamone. 

most of the lagunes on the coast are alternately completely separated 
from the sea, and united with it by temporary embouchures of incon- 
siderable depth. When the mass of rain-waters has flowed away, the 
breaches in the broken bank are instantly restored by the waves. In the 
same manner, on the shores of seas with strong tides, a number of rivers 
ai'e alternately canals of almost stagnant water, which a bank of sand 
separates from the ocean, and vast estuaries up which a powerful tide 
from the open sea flows. Thus the Bidassoa, separated from the gulf at 
low water by most gracefully curved sand-banks, is at the hour of high 
water an arm of the sea, from two to three miles wide. Almost all the 
small water-courses which discharge themselves into the Atlantic are al- 
ternately rivers and marshes twice a day. Even the Orne itself,. whose 



CONSOLIDATION OF LAGUNES. 



161 




Fig. TO. — Mouth of the Bidassoa. 

large delta spreads like a fan beyond the coast-line, is lost in a shingle- 
bank at the hour of \^ water. 

If the permanent or periodical water-courses open for themselves a 
gftssage through the bank, these very rivers, on the other hand, serve to 
bring the inland shore and the sea-shore gradually closer together by de- 
positing their alluvium in the interior lagunes. The reeds and other 
plants which delight in the turbid waters contribute also to the trans- 
formation of the ancient bays into marshes and firm ground. Beds of 
vegetable detritus, accumulated in the bays during a succession of years 
and centuries, rise in time above the ordinary level of the waters ; and 
then come great trees which solidify the soil, and attach it definitively to 
the continent. In the tropical regions, it is the different species of bao- 
bab and mangroves that aid most in the formation of the new shores. 
Raised on the scafiTolding of their high roots, like aerial buttz'esses one 

11 



162 



THE OCEAN. 



above another, they grow in the midst of the lagune. Hidden by the 
floating forest, the muddy liquid is soon filled with rubbish; the branches 
and uprooted trunks of the trees, being much heavier than the water, in- 
cessantly raise the bottom, and end by appearing on the surface. A new 
vegetation immediately takes possession of this yet undecided shore. 




* "Mei-viKe 



Fig. 71.— Mouth of the Orne. 

The same hydrological laws which determine the formation of banks be- 
tween two capes are at work to bring about the same result between two 
islands, or an island and the main-land. On the coasts of Europe a great 
number of coast-lands have thus lost their insular character, and are 
changed into peninsulas; the strait has. been gradually changed into an 
isthmus. The peninsula of Giens, between Hyeres and Toulon, jsresents 
a remarkable example of this transformation. It ft connected with the 
continent by two banks of fine sand, above three miles long, each devel- 
oped in regular curves, which turn their concave faces toward the op^ 
sea. Between these two banks stretches the vast lagune of Pesquiers. 
At the sight of this inland sheet of water and these low shores, hardly el- 
evated above the level of the Mediterranean, one can not doubt that the 
mountainous peninsula of Giens was formerly an island like Porquerolles 
or Port-Cros, and that the two roads, now separated, of Hyeres and Giens, 
were formerly one strait. The two uniting banks which joined the an- 
cient island to the coast of Provence, have been raised by the waves in 
the same manner and on the same plan as the coast ridges of the conti- 
nent. As to the diiferences of appearance, they can all be explained by 
local circumstances. Thus the bank which the isthmus of Giens turns to- 



FOBMATION OF PENINSULAS. 



163 




Fig. T2.— Peninsula of Giens. 

ward the west is composed in reality of two unequal fragments, due to 
the existence of a submarine reef which breaks the force of the waves at 
a little distance from the strand. It is equally to local causes that we 
must attribute the inequality of thickness presented by the two ridges of 
the isthmus. Undoubtedly the eastern bank owes its greater solidity and 
, height to the double action of the marine curi-ent that tends from east to 
west, and of the mistral which blows the opposite way in the direction 
from north-west to south-east; the two contrary forces have left as wit- 
ness to their strife this rampart of sand and debris. 



r~ 



l^^,^^ 



tunes Umt t/ / 



Fig. 73 Section across tlie Peninsula of Giens. 



The peninsulas of Cape Sepet, near Toulon, of Quibei'on, in Brittany, of 
Monte Argentaro, on the coasts of the Tyrrhenian Sea, and others less 
known, have been united to the continent by similar connecting cause- 



164 



THE ocean: 



ways analogous to those of Giens, There, too, the two armies of waves 
which break in the midst of the strait have gradually erected between 
them a double wall of separation, consisting of banks of sand and shingle. 
There, too, the two semicii-cular jetties have drawn nearer together in their 
central convexity, and the two triangular spaces, which separated the re- 
spective extremitie^l have at first been occupied by lagunes. In our days, 
most of the ponds, gradually filled up by sand, have been transformed 
into marshes or covered by dunes ; the two littoral ridges have been min- 
gled in a single one. Thus, the narrow isthmus of Chesil Bank, which ex- 
tends over a length of sixteen miles, between the coast of England and 
the former island of Portland, is composed of a single bank of shingle. 




T/ie^ Dcpt^ are> expressed^ vi' fcMnms.. 
Fig. T4.— Peninsula of Cape Sepet. 

In the same manner, the two French islands of Miquelon, near Newfound- 
land, which were still separate from each other in 1V83, have been united 
since 1829 by a rampart of sand, which the waves of two opposite gulfs 
have erected conjointly,* Guadaloupe is likewise an example of this phe- 
nomenon of junction between two lands of distinct origin. The range of 
volcanic mountains which rise to the west is united to the low island of the 
east, and the two islands are now joined to each other by a marshy plain, 
where the waters of the small canal, called the Salt River, stagnate. In 
the two islands of Choa-Canzouni, bathed by the waters of the Indian 
Ocean, an analogous phenomenon is presented, but there the connecting 
bank between the two islands is reduced, so to speak, to a mathematical 
point. 

M. Elie de Beaumont estimates the length of the coasts which owe their 
present configuration to banks of shingle and sand to about one-third of 
* Brue, Bulletin de la Societe de Geoc/raphie, 1829. 



C OAST-RID OES AND SAND-BARS. 



165 



the tolal development of the continental shores. It is in these basins 
with slight tides that these ridges present the most considerable dimen- 
sions. In France, all the shores of the Gulf of Lyons, from Argelez-sur- 
Mer to the mouths of the Rhone, form a series of coast-ridges, only inter- 
rupted by the rocks of Leucate, of La Clape, Agde, and Cette, and devel- 
oped in a vast semicircle nearly one hundred and twenty-five miles long. 



i" So W.ot Parts- 




it^J&'^flfniyif> 



Fig. 75.— Chesil Bank. 

The numerous ponds or etcmgs which it now separates from the Mediter- 
ranean, and which the alluvium of the rivers, the marine sand, and invad- 
ing agriculture, are unceasingly transforming into solid earth, were doubt- 
less so many bays along the base of the hills of Languedoc. Even since 
the historical epoch, these inland waters have notably diminished in ex- 
tent, and vast gulfs, changed into marshes, to the great detriment of the 
public health, have poisoned the atmosphere with their miasma. That 
which contributed most actively to the diminution of the surface of the 
pools were the graus, or passages by which the water of the sea brought 
in heaps of sand during tempests. These openings, some temporary and 
others permanent, but enlarging and diminishing by turns, and changing 



166 



THE OCEAN. 




Fig. 76.— Miquelon Isles. 



place, now in one direction and now in another, do not cease to modify 
the condition of the Hangs and countries on the coast. Here they allow 
masses of water to break through, which submerge the shores and exca- 



COAST-RIBGES AND SAND-BARS. 



1G7 




Fig. 77.— Coast-ridges between Port-Veudres and Aigues-Mortes. 

vate the soil, and elsewhere they are obstructed, and spread banks of fetid 
mud, as far as the eye can seQ, before the villages of the coast. In order 
to prevent for the future the transformation of the etaiigs into mud and 
marshes, M. Regy has proposed to replace the old tortuous graus by chan- 
nels for drainage, which, during the fine weather, allow the lacustrine wa- 
ters and those of the sea to communicate freely, but the sluices of which 
would be closed during storms, 

. The licU of Comacchio, as well as those of Venice, and of the ancient 
city of Aquileia, restrict the basin of the Adriatic, which formerly pene- 
trated much farther into the lands to the west and north-east. On the 



168 THE OCEAN. 

. 4 

southern coasts of Brazil and the Guinea coast, the littoral ridges thus 
cut olF considerable ti-acts from the ocean ; but nowhere are these levees 
of sand seen more numerously and better developed than around the Gulf 
of Mexico, and on the eastern coasts of the United States. We may say 




Fig. 78.— Lagunes and Lidi of Venice. 

that over a length of about 2500 miles the outline of the American conti- 
nent is formed of a double coast, the one bathed by the sea and the other 
by the interior lagunes. In front of the ancient coast, with its irregular 
indentations, the new shore describes its graceful curves from promontory 



ITieOceaii.&c HEADLANDS OF NORTH CAROLINA 



PL.X. 



"%, Eort Moivno 

'•'^ Cape Henry 

NORrOLK /\ 




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A 



\A 



^^sn^^I^E Sojj 



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2) 






5^ a]- \V' 



p A 



>i 



■A ^c^, 



O 

Cape Batteras 



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J.J 



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Cacpe Looliout 



Engrav^ by Erh ar d 



i,/t5o,ooo 
O 5 to ZO 30 40 



SANB-BANXS OF TUB BALTIC. 109 

to promontory, and, not even allowing itself to be arrested by the mouths 
of the rivers, stretches across the outlets in dangerous bars. 

Thus the indented coasts of North Carolina, and the ramified gulfs 
which cut into these peninsulas, and are prolonged even into the interior 
of the land in the form of marshes, are masked on the side next the sea 
by a natural bank nearly 220 miles long, against which the most fearful 
waves of the northern Atlantic break. These banks so gracefully curved 
are not constructed by the sea alone. They are due also to the pressure 
of the fresh waters brought from the Alleghanies by the Neuse, the Tar, 
the Roanoke, and other rivers ;* the direction of the breakwaters indicates 
precisely the line of equilibrium between the marine and fluvial waters. 
Within the outer coast-line it has been jjossible, without any considerable 
artificial means, to pi;t the whole series of interior lagunes in communica- 
tion with one another, and thus to allow ships to make long sea-voyages 
completely sheltered from storms. Even the marigots of Guinea, which 
spread parallel to the shore, have at all times served to facilitate traffic 
between the peoples of the coast ; but it is said that these marshy canals 
are gradually being filled up, either by the activity of the vegetation, or 
because of the sand which the wind of the desert transports thither.f 

Much less extensive than the banks of the Gulf of Mexico and of Caro- 
lina, those of the Eastern Baltic are not less curious by the geometrical 
regularity of their forms, and, besides, they have been the object of long 
and serious study. Three great rivers — the Oder, the Vistula, and the 
Niemen — discharge themselves each into a vast lagune, or Saff {hafen, 
port), which a narrow tongue of lands, called there a N^ehrung, separates 
from the oi^en sea. The Ac/jf' of the Oder, the entrance to which is guard- 
ed by the town of Swinemiinde, is already in great part filled up by mud. 
The Gtiriche Saff., or haff" of Courlande, is much freer from alluvium, and 
the Nehrung which deferlds it is a narrow sand-bank about sixty-eight 
miles in length. The central haff, known under the name of the Frische 
IIaff\ is protected by a bank similar to that of Courlande, but still more 
regular. All the western part of the estuary has already been filled up 
by the alluvium of the Vistula, the waters of which have opened a way 
through the bank. This embouchure has often changed its jilace. Till 
the fourteenth century it was to the north of the present passage, near 
Lochstadt (town of the gap, or grau). Later it opened at Rosenberg, 
nearly in the middle of the dike. To preserve their commercial monopo- 
ly, the merchants of Dantzic filled this opening up by sinking five ships 
there ; but another passage was formed almost immediately at a liltle dis- 
tance toward the north, near the castle of Balga. More greedy than wise, 
the Dantzicers again attempted to arrest the waters of the Vistula, and 
closed the passage of Balga. It was then that the Nehrung was broken 
before Pillau. Since this pei'iod the passage has not been sensibly dis- 
placed, and Pillau has always remained the port of the Frische Haff. 

* See the section entitled Rivers. 
Borghero, Bulletin de la Societe Geographic, July, 1866. 



ivo 



THE OCEAN. 




Fig. T9. — Coasts of Dantzic and Pillau. 

To the north of Dantzic a curious bank, twenty miles long, unites the 
main-land to the picturesque island of Hela (the holy). Doubtless the an- 
cient inhabitants of the country experienced a sentiment of religious ter- 
ror at the sight of the rude waves which assail this wooded hill, united 
to the continent by this narrow dike of sand stretching far away into the 
dim distance. 

It is to the same order of' phenomena that we must refer the gradual 
prolongation of tongues of land, which, bathed on either side by a cur- 
rent, project to a great distance into the open sea, owing to the fresh ma- 
terials which each new tide adds to the terminal point. It is thus that 
in less than sixteen years Cape Ferret has advanced about three miles 
across the channel by which the basin of Arcachon communicates with 
the open sea. In 1768 the cape was almost to the west of the basin prop- 
erly so called. In the latter part of the eighteenth century, and at the 
commencement of the present, the winds from the north, which blow in 
those parts more frequently than the other atmospheric currents, had 
caused the dunes of the promontory to advance each year in a southerly 
direction, while the surf from the open sea, and the ebb of the basin, in- 
cessantly added fresh masses of sand to the point. In fifty-eight years, 
from 1768 to 1826, the cape lengthened by above three miles toward the 
south-east, with an average speed of ninety-four yards per year, or about 



SANB-K'iyKS OF THE BALTIC. 



171 




Fig. SO.— Different positions of Cape Ferret from 17C8 to 1863. 

eight to ten inches per day. The point increased, so to say, visibly ; but 
a few years later the passage had suddenly changed its direction, and 
tending to the north, the tidal current commenced to wear away the pe- 
ninsula, and gradually caused it to retreat toward the north-west. In 
1854 the extremity of the cape had retrograded nearly one mile and a 
quarter. It is said that it is at present nearly stationary ; but if the chan- 
nel moves toward the south, which may happen any day, it is not to be 
doubted that the point of the cape would recommence encroaching upon 
the sea in the same direction. 



172 



THE OCEAN. 



CHAPTER XXI. 

SHALLOWS OF THE COAST. DEPOSIT EEOM CALCAREOUS EOCKS. — APrEAE- 

ANCE OP STEANDS AND BEACHES. 

The formation of shallows and sand-banks is connected also with that 
of littoral ridges ; they are developed parallel to the shore, under the 
combined influence of the currents along the coast and winds from the 
open sea, A glance at a chart which indicates the form of those ram- 
parts hidden under the waves, shows at once that all these invisible banks 
of sand and mud tend to elongate themselves in a straight line, or to fol- 




Eig. 81.— Eoad of La Madeleine, California. 

low graceful curves no less regular than those of the littoral ridges. In 
all the gulfs and straits on the coasts of California, the Carolinas, and 
Brazil, in the Channel and in the North Sea, there exist along the coasts, 
a multitude of these banks, the arrangement of which indicates exactly 
the path of the contrary or parallel currents which have been formed by 
their meeting. Their depth varies. There are some over which large 



Sff ALLOWS OF THE COAST. 



173' 



ships can sail without danger; but there are others very near to the sur- 
face of the water, over which the waves incessantly break. It is these 
banks, hardly below the level of the sea, which are the most dreaded ; 
and the English and American sailors, thinking of the fate that perhaps 
awaits them on these hidden sands, have gayly given them the ironical 
name of "frying-pans." In wide-mouthed gulfs and along straight coasts 
the sea endeavors to construct new shores by means of deposits of mud. 
The remains of sea- weed and animalcule, mixed with sand and clay, are 
deposited in deep layers on the coast, and cause the outline of the shores 
to advance gradually. Mud has been accumulated by hundi-eds and tens 
of thousands of millions of cubic yards since the historical era in the 
ancient Gulf of Poitou, in the Gulf of Carentan, situated at the foot of 




Fi?. 82.— Gulf of Carentan. 



the peninsula of the Cotentin, in the bays of the Marquenterre and of 
Flanders, in certain estuaries of the Netherlands and fff Friesland. In 
these parts the sea and the land are mingled ; the sea, gray or yellowish, 
resembles an immense slough, and continues the oozy surface of the 
shores. One does not know where the water terminates, or where the 
plain of mud, incessantly stirred by the tidal wave, begins. Still, the 



174 THE OCEAN. 

mud which emerges at low water is, little by little, hea|)ed up and con- 
solidated ; a species of conferva covers its surface with a slight carpeting 
of a pink hue ; then come the herbaceous salicorriia, which contribute to 
elevate the soil by their stiff branches springing from the stem at right 
angles. To this first vegetation succeed other marine plants — carices, 
plantains, reeds, and climbing trefoil. Then is the time to recover the 
oozy meadow for agi'iculture, and to connect it with the main-land by 
defending it with strong dikes against the assaults of the sea.* 

In the seas whose waters have a high average temperature, the waves 
do not confine themselves to constructing littoral ridges and filling up 
the bays ; they even build actual ramparts of stone. In consequence of 
the rapid evaporation produced by the rays of the sun, the calcareous 
particles and mud contained in the water are gradually deposited along 
the shores and over the base of the promontories. Mixed with sand and 
fragments of shells, it tends to form solid shores with regular contours. 
On the Atlantic coasts of France — at Royan, for example — one can here 
and there already observe some formations of this kind ; and farther to 
the north, at Elsinore, some of these stones have been discovered, contain- 
ing ancient Danish coins.f On the French shores of the Mediterranean 
these modern rocks are very numerous, and in a short walk one can often 
collect a large quantity of sandy blocks and various conglomerates, 
united by calcareous substances, and' containing multitudes of broken 
shells. The Museum of Montpellier possesses a c&nnon which was dis- 
covered near the principal mouth of the Rhone, imbedded in a calcareous 
deposit. On the northern coasts of Sicily, where the mean temperature 
of the waters rises to 64'4° Fahr.,the stones and pebbles of the shore are, 
in many places, agglutinated by calcareous cement.J In the same way 
the fragments of rocks, which the torrents of Arabia Petraea bring every 
winter from the top of the mountains to the shores of the Red Sea, are, 
in the space of a few weeks, converted into a stratum of solid conglom- 
erate. Every year a new layer of stone is added to the old ones, and in 
future centuries we shall be able, perhaps, to estimate the age of the for- 
mation by the number of its beds, one above the other, in the same way 
as we recognize the age of a tree by the number of its annual rings of 
wood.§ 

We must explore the shores of the Antilles, or other tropical seas, to 
observe this phenomenon of the formation of rocks in all its grandeur. 
There the waves, heated to 89-6° Fahr. by the rays of a vertical sun, de- 
posit limestone in sufficient quantity notably to increase the extent of the 
shore. The tufa of Guadaloupe, in which the famous human skeleton ex- 
hibited at the British Museum was found, belongs to this recent forma- 

* Emile de Laveleye, Revue des Deux Mondes, November 1, 1683. Von Maack, Zeitschrift 
fur die allgemeine Erdhunde, January, 1860. 
t Von Hoff, Verdnderungen der Erdoherftiiche, tome iii., p. 311. 
X De Quatrefages, Souvenirs d'un Naturaliste. 
§ Marsh, Man and Nature, p. 455. 



DRYING UP OF BAYS AND SALT LAKES. I75 

tion. It grows, so to say, under the very eyes of the observer, ana grad- 
ually covers with a rocky crust all those objects which the sea rejects, 
and which the brooks bring d6wn from the interior. In many parts of 
terra firma these quarries of marine stone are actively worked for build- 
ing towns' on the coast, and all the excavations made in these banks of 
limestone are soon filled up by new materials. The quarry grows under 
the laborers who are occupied in detaching the blocks ; hence the name 
oi Mag,onne-bon-dieu, which the natives have given to those rocks which 
seem to be renewed of themselves. 

On the shores of Ascension Island Mn Darwin found some of these con- 
glomerates cemented by marine limestone, whose specific weight was 
2'63 — that is to say, hardly less than that of Carrara marble. These beds 
of compact stone, deposited by the sea, contain a certain quantity of sul- 
phate of lime, as well as the animal substances which are evidently the 
coloring principle of the whole mass. Sometimes the translucid stucco 
covering the rocks has the polish, hardness, and hue of nacre ; moreover, 
as chemical analysis proves, this kind of enamel and the envelope of liv- 
ing mollusks are composed of the same substances equally modified by 
the presence of organic matter. Mr. Darwin has seen some of these cal- 
careous deposits, whose composition and nacreous appearance seem as if 
they ought to be attributed to guano saturated with salt-water.* 

This construction of new shores, either by the sea itself or by the coral 
animals, like the gradual' formation of the dunes, results in completely 
modifying the form of the coast, by separating from the rest of the sea 
large bays, which the rapid evaporation transforms later into fii-m land. 
It is thus that on the eastern coast of Africa the small Lake of Bahr-el- 
Assal, at the extremity of the Gulf of Tedjura, has been separated from 
the sea by a slender ridge of sand, and dried up under the rays of the sun. 
Rain-water being very rare in this country, and the basin receiving no af- 
fluent, its waters have not been replaced, and now it is only a marshy hol- 
low, the level of which is about "five hundred and seventy feet below the 
Red Sea.f While they occupied the coast of Abyssinia during the last 
war, the English engineers discovered another basin, dried up and com- 
pletely covered with salt, which was one hundred and eighty-nine feet 
below the sea-level. It is very probable, too, that the dej)ressions in 
which the great river Haouach loses itself to the south of the j)lateau of 
Plabesch are likewise below the sea-level. The Isthmus of Suez formerly 
ofiered a phenomenon similar to that of the Bank of Tedjura. There, too, 
a lacustrine sheet, which j^reviously formed part of the sea, had been in- 
closed by the littoral ridges, and had almost entirely evaporated. Only 
in our days the grand inter-oceanic canal causes the marine waters to flow 
again through this dried-up lake. The ancient banks on the shores of the 
Mediterranean and the Red Sea, which the forces at work in the interior 

* Darwin, Volcanic Islands, p. 49, and following. 

t Rochet A^Hericom't, Voyage au Choa. Christophe, Jowrna/ of the Geographical Societi/, 
vol. xii. 



176 



THE OCEAN. 



WT.<>\'eai-& 



o 



*"" ^ t^ 



^ 









^ 














Fig. S3.— Bahr-el-Assal and the Gulf of Tedjura. 

of the planet had gradually elevated to the height of several yards,* have 
been pierced by engineers, and an artificial strait much more important 
for human progress than the great arm of the sea was formerly, joins the 
Mediterranean with the Arabian Gulf 

If the great geological labors of the ocean, such as the erosion of cliffs, 
the demolition of promontories, and the construction of new shores, aston- 
ish the mind of man by their grandeur, on the other hand, the thousand 
details of the strands and beaches charm by their infinite grace and mar- 
velous variety. All those innumerable phenomena of the grain of sand 
and drop of water are produced by the same causes which determine the 
great changes of the shore. At the sight of the delicate lines which the 
dying wave traces on the beach, as well as in the presence of the wild 
coasts which the surf wears away in fury, we feel ourselves brought back 
by various impressions to the contemplation of the same general laws. 
Each wave accomplishes on its little portion of the shore a work similar 
to that of the great ocean on the outline of all the continents. . In a space 
* See the section entitled The Slow Oscillations of the Terrestrial Soil, 



VARIED ASPECTS OF THE SHORES. I77 

of only a few yards wt can see the regular curves of small bays round 
themselves, littoral ridges rise, inland lagunes fo^-m, and cliffs of shells and 
fuci being eroded. At the extremity of certain sheltered bays — in the 
Bay of Beaulieu, near Nice, for example — black masses of from three to 
four yards in height may be seen, cut into peaks and pierced with caverns 
like rocks; these are masses of algae. 

Among the various marvels of the shore nothing astonishes us more at 
first? than the designs traced on the sand, often with perfect regularity. 
Every breaker brings with it shells, pebbles, and other fragments of all 
kinds and of difierent sizes. These objects are so many little reefs which 
divide the wave on its return to the sea, and cause it to trace upon the 
ground a net- work of intersecting lines. The surface of the strand pre- 
sents in consequence an interlacing of innumerable lozenges, all orna- 
mented with a shell or pebble at their upper end, and pointed or slightly 
rounded. All these little lozenges are themselves comprised within large 
quadrilaterals formed by furrows, having, as starting-point, an object of 
relatively considerable dimensions. Contrasts of colors aid in the relief 
to vary still more this varied aspect of the shore. The differently colored 
materials being, in general, of a different specific weight, are distributed 
in a regular manner in the various parts of the lozenges. One side of the 
figure may be formed of small crystals of mica, while another is composed 
of black sand charged with j^eat, another of pink or yellowish shells, and 
the fourth of grains of a pure white. Sometimes the sand, impregnated 
with organic substances, shines like watered silk, or is slightly iridescent, 
as if a very thin layer of oil were spread over the ground. 

All these hues modify the aspect of the shores infinitely, and the greater 
or less inclination of the ground introduces yet a new element of variety 
into the net- work of lines. In all those pRces where the slope is consid- 
erable, the water hollows out the sands in the figure of miniature rivers 
with their tributaries and deltas. Besides, these small hydrographic sys- 
tems themselves differ from one another according to the inclination of 
the ground and the weight of the grains of sand. In one place the slop- 
ing ground and the fineness of the displaced materials permit drops and 
streamlets of water to descend in a straight line toward the sea ; in an- 
other the rivulets, making their way with difficulty between the obstacles 
that arrest them, flow in winding courses. Elsewhere, water-courses can 
not even be formed. The water of the sea remains on a horizontal strand, 
and all the wavelets reproduce, in hollows or in relief on the sand of the 
bottom, all the movements which the breath of air impresses on them. 
There is no appreciable difference between the varied surface of the shore 
exposed freely to the wind and that of the sand which a thin watery bed 
covers, excepting perhaps that the furrows of the pool are more regular 
and deeply hollowed out. 

Among the innumerable phenomena that might keep a geologist all his 
lifetime on the sea-shore, we must include a kind of miniature volcano. In 
breaking regulai'ly on the shore, the wave brings each time a certain quan- 

12 



178 THE OCEAN. 

tity of sand which it spreads in a thin layer. The*air absorbed into the 
pores of the soil immediately disengages itself in bursting bubbles ; but 
here there are always^ a great number of aerial particles which can not 
penetrate the damp bed of sand, and remain inclosed. Under the influ- 
ence of the warmth of the ground or of the surrounding air, these parti- 
cles dilate little by little, the pressure of the gas raises the hardened coat- 
ing, and forms a cone, which sometimes bursts in consequence of the in- 
ward pressure, and throws out in volleys little spouts of sand-grains. It 
is true that unobservant persons walk over millions of these humble vol- 
canoes without perceiving even one, but those who love the earth under 
all its aspects, and who contemplate with the same admiration the grain 
of sand and the mountains, can easily discover and study them. For the 
naturalist, who sees immense forests in every heap of algae, and a world 
of animals in the remains which strew the sand, the thousand wonders of 
the shore can not fail always to awaken an intense pleasure. 



OBIQIN OF ISLANDS. 179 



CHAPTER XXII. 

ORIGIN OF ISLANDS. — ISLANDS OF CONTINENTAL OEIGIN. — KOCKS OF THE 
SHOEES. — ISLANDS OF DEPRESSION, ELEVATION, AND EROSION. — ISLANDS 
OF OCEANIC ORIGIN. — ATOLLS AND VOLCANOES. 

On viewing the great geological labors accomplished by the dash of 
the waves on the various coast-lines, savants have often asked what is the 
share the sea takes in the formation of islands. Among the lands which 
are scattered over the surface of the ocean, some disposed in groups or 
series, and others completely solitary, how should we distinguish between 
those which the sea has detached from the continents, and those which 
have existed in an isolated manner from all times like separate worlds? 
Is it even possible, in the present state of science, to attempt a classifica- 
tion of islands, according to their origin ? Yes, this work may be com- 
menced. By calling to our aid the new resources which botany and zool- 
ogy offer to physical geography, we may affirm that, sooner or later, we 
can indicate with certainty the manner of formation, and the relative age 
of each oceanic country.* 

Firstly, it is evident that the islands, islets, and rocky ledges situated 
in the immediate neighborhood of the coasts are a natural dependency of 
the continents, and geologically make a part of them. At the base of the 
high mountains, which send far into the sea advanced capes similar to the 
roots of an oak, we may see in many places, so to say, the crests of the 
lateral chains continue under the surface of the ocean. The outline of the 
continental heights sinks by degrees ; to the mountains succeed the hills, 
and the promontory of rocks, whose escarpments plunge beneath the even 
surface of the waters. An inconsiderable strait, simply a hollow where 
the waves meet each other, separates the cape from a less elevated island. 
But farther on there opens a wide channel, and the peak which shows it- 
self at the surface on the other side of the submai'ine valley is no longer 
any thing more than a needle of rock. Beyond stretches the open sea 
where the submerged ledges, if any still exist, are only revealed by the 
whitening foam. On all the abrupt coasts these islets belonging to the 
primitive architecture of the continent are very numerous, and even in 
certain parts form real archipelagoes. Norway, Western Scotland, Chilian 
Patagonia, and all those countries where the fjords change the coast-line 
into an immense labyrinth, are thus bordered with innumerable islands, 
having likewise*their indentations, their straits, and their girdles of islets. 
This is because, Since the relatively recent retreat of the glaciers which 
filled all the space comprised between the circles of snowy plateaux and 

* See especially the. works of Darwin, Wallace, and a study by M. Oscar Peschel, der Ur- 
sprung der Inseln ; Ausland, January and February, 1867. 



180 THE OCEAN. 

the exterior promontories, the original relief has but slightly changed. 
The terrestrial alluvium brought down by the torrents has only filled up 
a small number of valleys ; and the bases of the islands and capes, plung- 
ing deeply into the waters, have not served as support to marine alluvium 
similar to that which spreads along the low coasts. Isolated rocks, which 
the ice formerly surrounded as it now surrounds the " Jardin" of Mont 
Blanc, now rise in the midst of the waters, but they are not the less the 
salient points of the continental relief; in shallower waters, where the de- 
posit of the marine alluvium would be easily accomplished, they would 
long since be joined to the shore. 

Among the islands which may be considered as simple dependencies of 
the great neighboring lands, we must also class not only those which the 
marine or fluvial alluvium has raised, simple emerged banks which are es- 
pecially found along low coasts and near the mouths of rivers ; but like- 
wise the islands which are due either to the rising or gradual sinking of 
the ground. Thus, the chain of insular downs which defends the coast-line 
of Friesland and Holland against the assaults of the North Sea, from Wan- 
gerooge to the Texel, is most certainly the remains of the antique shore ; 
and it is this rather than the half-submerged beaches of the Dollart and 
the Zuyder Zee which marks the true boundary between land and sea.* 
On the other hand, the coasts of the Scandinavian peninsula, which rise 
slowly above the waves, have been enriched with new islands during the 
course of the present geological epoch. In the maze of the Norwegian 
fjords, in the Lofoten Isles, in the archipelago of the Quarken, hidden 
ledges have become visible rocks, then extensive islands, where the algae 
have been gradually replaced by a terrestrial flora. While the continent 
was encroaching upon the sea, the islets here and there have risen up and 
spread far over the waters like the leaves of some gigantic plant. The in- 
sular rocks rise slowly from the depths of the ocean, elevated by the same 
force which raises the neighboring continent. And is not a like phenome- 
non accomplished on the coasts of Scandinavia ? Perhaps even the large 
island of Anticosti, which extends in the Gulf of St. Lawrence over a 
length of more than a hundred and twenty-five miles, is one of these slowly 
elevated lauds, for, according to the testimony of Professor Yule Hind, one 
does not find in the granitic valleys of its rocks either serpents or batra- 
chians, as on the coasts of Labrador and Canada. If it is really thus, we 
could hardly admit that Anticosti has ever been in communication with 
the continent of America; it must have emerged^from the waters like the 
islets of the Scandinavian coast-line. 

It has happened differently with regard to Great Britain and the great- 
er part of the islands which fringe the outline of the continent. It is cer- 
tain that England formerly made a part of Europe. Tiiis is proved by 
the perfect agreement between the shores on each side of the Straits of 
Daver ;f it is also proved by the fauna and the flora of the British Islands, 

* See above, p. 154. 

t See the section entitled The First Ages, and above, p. 27. 



ISLAMDS OF CONTINENTAL ORIGIN. 181 

ill which all the auimals and all the wild flowers are colonists from the 
neighboring world; not a single species belongs peculiarly as its own 
production to the soil of old Albion.* In the same manner, Ireland has 
been separated from Great Britain during the present geological period, 
and around the two principal islands a number of secondary fragments — 
the Isle of Wight, Anglesea, and the Scilly Isles — have been similarly iso- 
lated in the midst of the waves. 

A multitude of islands, situated, like England and Ireland, in the neigh- 
borhood of continents, are also simply fragments which the waves, aided 
perhaps by the gradual sinking of the land, have detached from the 
shores of the main-land. The magnificent Archipelago of Sunda, the Mo- 
luccas, and the neighboring islands of Australia, present the most remark- 
able example of this breaking into jDieces of the continental masses. A 
channel, nearly nineteen miles wide, and more than one hundred and nine 
fathoms deep, passes between the two large islands of Borneo and Cele- 
bes, and, continuing in a southerly direction, separates the two volcanic 
countries of Bali and Lombok, very near to each other. This channel is 
the ancient strait which served as the common limit to Asia and the 
southern continent. To the west, Java, Borneo, Sumatra, the peninsula 
of Malacca, and Cambodia, rest on a submarine plateau, which lies hard- 
ly thirty-three fathoms below the surface of the waters : to the east Sum- 
bava, Flores, Timor, the Moluccas, New Guinea, and Australia, are like- 
wise on a sort of pedestal, which sinks gradually, and upon which the 
zoophytes construct here and there long barrier reefs. Thus, a|Lthe natu- 
ralist Wallace has demonstrated by his researches in the Indian Archipel- 
ago, all the species of plants and animals differ completely on each side of 
the dividing channel. The fauna and flora are Asiatic to the west, while 
to the east they present the Australian type ; even the birds, for whom a 
strait a few leagues in width would seem but a slight obstacle, are dis- 
tinctly different in each of the two groups of islands. 

We must, therefore, see in the Australian archipelagoes the wreck of a 
great continental mass, which must have divided into numerous frag- 
ments at epochs more or less distant from our time. We may say as 
much of the islands of the ^gean Sea, of those of Denmark, of the Polar 
Archipelago, of the New World, of the maze of the Magellanic Islands, 
and of the greater part of lands which surround the shallower waters in 
the neighborhood of the coasts. As to the great islands of the Mediter- 
ranean — Cyprus, Crete, Sicily, Sardinia, Corsica, and the Balearic Islands 
— they are also very probably the remains of more extensive countries for- 
merly united to those continents now known as Europe, Asia, and Africa. 
For though these lands, with the exception of Sicily, all rise from the 
depth of abysses having, on an average, from 500 to 1000 fathoms depth, 
nevertheless the fossil and living species of the Mediterranean islands do 
not differ from those of the neighboring continents, and it is consequent- 
ly there that we must seek their origin. From a geological point of 
* See the section entitled The Earth and its Flora. 



182 THE OCEAN. 

view, one can even say that the countries of the western basin of the 
Mediterranean, Spain, Provence, the Italian peninsula, Tunis, Algeria, and 
Morocco, form, with the neighboring islands, a whole much more precise- 
ly defined than, for example, Central Europe, from the Straits of Gibral- 
tar to the shores of the Caspian. In spite of the depths which separated 
them, the coasts lying opposite to each other, on each side of the Tyrrhe- 
nian Sea, have preserved a similarity of physiognomy in the flora and 
fauna of the land. 

The Mediterranean Islands may thus be considered either as dependen- 
cies of the neighboring continents, or, better still, as the remains of an 
ancient country partially swallowed up. Still, there exist in the midst 
of the sea insular masses in which geologists see nothing else than the 
witnesses of continental tracts which now have disappeared. Thus Mad- 
agascar, though sufiiciently near to Africa, seems a sort of separate world, 
having a flora and fauna belonging peculiarly to itself, and even possess- 
ing entire families, especially of serpents and lemurs, which have no other 
representatives in our planet. Strange to say, even the island of Ceylon, 
half united to Hindoostan by the rocks, islets, and sand-banks of the Pont- 
de-Rama, differs much from the neighboring peninsula by the general fa- 
des of its animals and plants, and we may question if, instead of being 
simply a dependence of Asia, it is not, on the contrary, the last remains 
of an ancient continent which extended over the area of the Indian Ocean, 
and comprised Madagascar, the Seychelles, and other islands now almost 
imperceptible on the map. 

Amon^ihe fragments of vanished worlds, we ought also probably to 
class the greater part of the Antilles and New Zealand. The larger An- 
tilles present a much more striking contrast with the countries of North 
America than that between Ceylon and the peninsula of the Ganges. By 
elevation and geological character, Hayti and Jamaica do not in any wise 
resemble the low lands of the American coast, situated on the other side 
of the gulf; their vegetable and animal species differ" notably from those 
of the neighboring continent, though winds, currents, birds of passage, and 
even man, have worked together for an unknown number of centuries to 
carry animals and plants from one shore to the other. As to New Zea- 
land, it is quite a distinct world, whose flora and fauna have an essential- 
ly original character. Neither the fossil nor the living species resemble 
those of Australia or South America.* And the greater number of sa- 
vants agree with the opinion of Hochstetter, who sees in New Zealand and 
Norfolk Island the fragments of a continent isolated ever since the com- 
mencement of the Mesozoic period. While Great Britain may be consid- 
ered as a type of the islands scarcely separated from the neighboring con- 
tinent, her fine colony at the antipodes represents, on the contrary, an 
ancient world, gradually reduced by subsidence and the erosions of the 
sea, to the dimensions of a mere insular group.' 

The present shape of islands often allows us to recognize what was their 
* See the sections entitled The Earth and its Flora, and The Earth and its Fauna. 



ANTiqUITY OF INSULAR LANDS. 



183 



earlier form when they extended over a much more considerable space. 
By their outline and ramifications, the mountain ridges indicate in a gen- 
eral manner the first Configuration : they ai'e as the fragments of a skele- 
ton around which we reconstruct, in thought, the contours of the ancient 
continental body. Besides, many of these, of which only the primitive 




84 Choa-Cauzouni. 



skeleton remains, and whose plains have disappeared, are indented in the 
most curious manner, and their shores often present the most fantastic 
outlines. Thus Choa-Canzouni, in the Archipelago of Comoro, is a group 
of two large islands, united by a sort of stalk ; Nossi-Mitsiou, in the same 
region, resembles a trunk with two broken boughs ; finally, Celebes and 



184 



THE OCEAN. 



Gilolo, so remarkable by the parallelism of their gulfs and promontories, 
seem to be both constructed on the same model; and what we know of 
the mountains of Borneo allows us to believe that if this large island were 
to be submerged beneath the sea, its shores would resemble, by their con- 
tour, those of its two neighbors in the sea of the Moluccas.* 




Fig. 85.— Nossi-Mitsiou. 

Besides these fragments of ancient ""or modern continental masses, all 

the projections which show themselves above the level of the ocean are 

either built by zoophytes, or else cast up by volcanoes from the bottom 

of the sea; one or the other is, without exception, the origin of all these 

* Oscar Peschal, Ausland, 1868. 



ORIGIN OF ISLANDS. 



185 



islands. The first, as we know,* are disposed in atolls^ or annular reefs, 
formed themselves of rings of smaller dimensions ; while cones of lava, that 
are elevated in the open sea, rise proudly above the waves, and reveal the 
independence of their origin by a declivity which is continued pretty reg- 




Fig. 86.— Celebes and Gilolo. 

ularly below the waters. Still we can see by the exan^ple of the volcano 
of Stromboli, and more plainly still by that of the island of Panaria, that 
the waves constantly lessen the submarine slopes by distributing to a dis- 
tance the lava and cinders rejected by the craters. 




Fig. ST.— Section of Stromboli, from S.W. to N.E. 

Compared with the lands of continental origin, the truly insular masses 
composed of .lava, or built 1^ the coral animals, have relatively a very 
slight extent. It seems that, according to the general arrangement of the 
globe, the separation must at first have been much more marked between 

* See the section entitled The Slow Oscillations of the Terrestrial Soil ; and below, that en- 
titled The Earth and its Fauna. 



THE OCEAN. 




Fig. 88.— Section of Pauaria, from N. W. to S.E. 

the sea and the emerged lands. On one side great continuous countries, 
on the other desert oceans, appears to have been the natural distribution. 
But the incessant work accomplished on our planet, as on all the stars of 
heaven, has infinitely modified the fiarm of the continental surfaces and 
the channels which separate them. In the same way as by its rains and 
snows the sea has scattered lakes over the regions raised above its level, 
and traced the innumerable valleys of the water-courses, so have the lands 
given to ocean those myriads of islands and islets which vary its surface 
so gracefully. The alluvium of the rivers, the erosive power of the waves, 
the internal forces, which slowly raise or depress vast countries, or cause 
cones of lava to spring up suddenly from the deep ; finally, the numerous 
organisms which assimilate the various substances contained in sea-water, 
have all worked in concert to scatter here and there islands of different 
forms and sizes, some in larger, and others in smaller groups, or even com- 
pletely isolated. Later, the winds, rains, monsoons, and other meteoric 
influences of the atmosphere ; the oceanic currents, the ebb and flow, the 
undulation of the waves, all which moves and floats in the water and in 
the air, birds and fish, sea-weed and drifted wood, foam and dust — have 
never ceased to act directly or indirectly, to introduce life into these isl- 
ands, to people them with species of animals and plants, and thus to pre- 
pare them for the abode of man. 



OlilGIN OF SAND-DUNES. 



BOOK v.— THE DUNES. 



CHAPTER XXin. 

DUNES BESTJLTING FROM THE DECOMPOSITION OF EOCKS. — FORMATION OF 
MOVING DUNES ON THE SEA -SHORE. — SYMMETRICAL DISPOSITION OF 
RIDGES OP SAND. 

It is principally upon the sandy beaches of the ocean that those chang- 
ing hillocks known under the nam'e of dunes rise in long rows. Never- 
theless, the phenomenon of the elevation of the sand in moving hills may 
also occur at a great distance from the present sea-shore. Dunes are 
formed on all points of the ^lobe where the wind finds and drives before 
it light sandy materials; but we must remark that these substances only 
exist in considerable quantities on the shores of the sea and large lacus- 
trine basins, at the bottom of ancient gulfs and straits transformed into 
deserts, on the banks of rivers, which roll sand along their beds, and 
which are exposed to frequent changes of level by the alternation of 
droughts and inundations. It is the waters which,* by their destructive 
action on the cliffs, prepare the sandy particles necessary for the construc- 
tion of dunes ; and this origin allows us to consider the shifting ridges of 
sand, whatever be their distance from the shore, as products of the ocean. 

In all the great deserts of Asia and Africa, we see some of these terres- 
trial waves caused by aerial currents.* Some exist also on the banks of 
the Nile and other great rivers. Even in France very fine dunes about 
thirty feet high rise on the banks of the Garden immediately below the 
celebrated Roman bridge; it is the mistral which has raised them. In 
leaving the gorge which incloses it, this wind seizes the particles of fine 
sand left on the shores and dried by the sun, and deposits them at the en- 
trance of the plain, where it spreads over a wider extent, and loses in in- 
tensity what it gains in surface. 

A certain number of dunes have been formed on the spot during the 
course of centuries by the disintegration of freestone rocks. Fogs, rains, 
frosts, and other atmospheric agents, gradually wear away the stone and 
transform it into sand, which falling, leaves fresh beds at the surface. 
These are subject in their turn to the destructive meteoric influences, and 
it is thus that the rock, once solid, is gradually changed, often to a con- 
siderable depth, into a mass of crumbling sand. The grains chafed against 
each other enuring their fall become finer and finer, and when the wind is 
high, it can carry away these sandy particles, cause them to ascend the 
* See the section entitled Plains. 



188 THE OCEAN. 

slope of the talus, and sometimes even raise them in clouds like the smoke 
of a volcano. Nevertheless, the dune, still enveloping a solid kernel, and 
composed in great part of grains heavier than those of the sea-coast, is 
not entirely displaced by the action of storms ; it only takes another form 
in consequence of the gradual change of its slopes. Several mountains 
of this kind near Ghadames, which were formerly rocky hills, rise to one 
hundred and fifty and six hundred feet high. One of them, which is not 
less than five hundred and ten feet, has an inclination of thirty-seven de- 
grees on the side exposed to the wind ; nearly the greatest slope that a 
talus of sand can present.* 

As to dunes properly so called, those which are found far in the inte- 
rior of continents can not be comjaared in importance with those which 
are developed in long ridges, parallel to the sandy shores of the sea. On 
the strands of the ocean which are not rocky the existence of dunes is al- 
most constant; the only low shores which are destitute of them are those 
which the waves have formed of clayey substances, of compact mud, or 
sand much mixed with animal and vegetable detritus. The sandy shores 
of the Mediterranean, of the Baltic, and other inland seas, where the tides 
are hardly perceptible, also present very insignificant dunes, because the 
want of ebb and flow does not allow the sand to acquire suificient mobil- 
ity. We see, however, some more than ninety feet high between Vera 
Cruz and Tampico, on the shores of the Gulf of Mexico, where the tides 
are very slight. On all oceanic coasts, the sand of which is loose enough 
to allow itself to be Mised by the wind, the formation of dunes is accom- 
plished with perfect regularity. 

These hillocks rising, so to say, beneath the very eyes of the observer, 
it is not difficult to follow their progress, nor to offer a theory regarding 
them. The waves constantly agitating the shifting foundation of the 
shore become charged with arenaceous matters, and spread then in thin 
layers over the strand. Then, at low tide, the grains of sand soon become 
dry, and cease to adhere to each other, and thus allow themselves to be 
carried toward the land by the wind from the open sea. These are the 
materials of dunes. If the shore rises toward the interior of the conti- 
nent in a perfectly even manner, this sand, cast up by the waves above 
the sea-level, and carried far by successive gusts of wind, would extend 
over the ground in layers of uniform thickness ; but the inequalities of 
.the surface prevent this. Pebbles, branches and trunks of trees covered 
with shells, plants and bushes with tough roots, project above the beach, 
and oppose the advance of the wind, which glides over the ground, carry- 
ing the grains of sand that have remained on dry land. These slight ob- 
stacles suffice to determine the origin of dunes by obliging the breeze to 
let fall the little cloud of arenaceous or calcareous dust with which it is 
charged. The horizontality of the shore is thus interrupted; rows of 
sandy knolls, which are subsequently to rise to real hills, commence to be 
traced upon the ground. 

* Vattone, Mission de Ghadames ; Barth, Zeitschrift fur die Erdkunde, March, 1864. 



FORMATION OF BVNES. 



189 



When the wind from the open sea blows with sufficient force, we can 
not only witness the growth of the dunes, but we can also aid in their 
formation, and verify by direct experiment the assertion# of theory. If 
we deposit some object on the ground, or, better still, thrust a row of 
stakes into the sand, perpendicularly to the direction of the wind, the cur- 




Fig. 89.— Formation of a Dune. 



rent of air which strikes against the obstacle will instantly rebound to 
form an eddy or whirl^sool, the diameter of which is always pro^^ortioned 
to the height of the stake. Arrested by this eddy, the grains of sand car- 
ried by the wind are gradually deposited on the near side of the barrier, 
till the summit of the miniature dune is on a level with the imaginary 
line leading from the shore to the upper end of the obstacle. Then the 
sand driven by the breeze from the sea, which ascends the inclined plane 
presented by the front of the hillock, no longer allows itself to be carried 
in the eddy and brought back. It crosses the little ravine which the gy- 
ration of the air has produced in front of the palisade, and falls beyond it 
to accumulate gradually on the other side of the obstacle, taking the form 
of a descending talus (Fig. 90). It is due to the knowledge of these facts 




Fig. 90.— Formation of Sand Dune 

that we are able to force the elements to construct a protecting rampart 
of dunes on various points of the coast threatened with erosion by the 
waves of the sea.* 

Such are always the commencement of dunes, whatever be the object 
which opposes itself to the wind. It is easy to convince one's self of this 
by the sight of the houses or huts which the custom-house officers and 
shepherds erect in the sandy hollows of the dunes of the Landes, not yet 
fixed by seedling trees. On the side toward the sea, which is also that 
from which the wind blows in terrible gales, the dwelling remains separa- 
ted from the talus of sand by a ditch of defense, as regular as if it had 
been hollgwed out by the hand of man ; but on the side which fronts in- 
land the sand is gradually heaped up, and if it is not swept away, does 
not fail to rise soon to the level of the roof 

On the slightly-undulating plateau which extends at the foot of the 
* See the .section entitled The Work of Man. 



190 THE OCEAN. 

grand j)yramicls of Egypt we can also study the same phenomena. The 
winds from the east and north-east, which strike against the eastern face 
of the enormoulhnasses of stone, rebounding and developing their reflect- 
ed waves on the ground, do not allow the sand to be deposited on the 
lower steps of the edifices. It is only at a certain distance, at the precise 
spot where the current is neutralized by the masses of air coming directly 
from the east, that the dunes can form. To the west of the pyramids, on 
the other hand, long mounds of sand, more or less inclined, support them- 
selves against the base of the monuments. In the same way, at the foot 
of certain cliffs of Liguria, where the sands accumulate in dunes, there al- 
ways exists a sort of trench between the rock and the moving heap. 

When the labor of man does not intervene to arrest the progress of the 
dunes formed on the sea-shore, the various obstacles which have deter- 
mined the accumulation of the sands disappear at first on the descending 
side under successive beds ; then, when this part is entirely hidden, the 
front begins to be buried in its turn. The wind, instead of developing 
itself according to a horizontal plane, as on the surface of the ocean, is 
obliged to take an oblique direction to ascend the slope of the dune. As 
soon as it is sufficiently elevated, the atmospheric current passes freely 
above the obstacle which arrested it before, the little eddy which re- 
volves in front ceases its gyrations, and nothing then hinders the sand 
from' gradually filling up the ravine which the aerial current had main- 
tained in front of the barrier. Soon the summit of the dune coincides 
with that of the obstacle: the latter disappears completely,|^nd the hil- 
lock, growing like a wave which approaches the shore, and constantly rais- 
ing its crest higher, which is incessantly displaced, continues to encroach 
upon the land. The various strata of sand which the wind from the open 
sea successively brings to the summits of the dunes, spread in .large sheets 
over the descending talus, and glide down to the base. In the Laudes of 
the Gironne the western slope of the dunes, whose base is not worn away 
by the sea, is, on an average, from seven to twelve degrees. The eastern 
slope, which is that of the descending talus, is from twenty-nine to thirty- 
two degrees ; that is to say, three times as great. It would be forty-five 
degrees if the rains did not make ravines in the talus, and thus prolong 
the inclination.* 

Thus the dunes incessantly gain, owing to the new layers of sand added 
to their changing talus. But the action of the prevailing wind does not 
limit itself to increasing them ; it ends by displacing them entirely, and 
making them, so to say, travel over the ground. The object at the base 
of which the eddy of air had deposited the first grains of sand is at length 
decomposed ; inclemencies of the weather, insects, moisture, and chemical 
agencies destroy it, and when it has disappeared the sand which it retain- 
ed shifts again. The wind, which only carried away the superficial beds 
of the dune to replace them incessantly by new sheets of sand, can now 
carry away all the anterior part of the hillock ; it lengthens the descend- 
* Raulin, Geographie Girondine. 



MARCH OF THE DUNES. 191 

ino' talus at the expense of the shore side, and the base of the hill, worn 
away by the wind, constantly retreats from the shore. The dune is on the 
march ; it advances inland. Such is the mobility of the sands that even 
when the waves erode the foot of the dune, and force it to fall into the sea, 
the summit does not the less advance toward the continent. Destroyed 
on one side it invades on the other, like those voracious insects which, 
even when cut in half, do not cease to eat. The high dunes of Lagrave, 
to the south of Archachon, are the most curious in this respect ; below, 
the sea forces them to fall in ; above, they bury the pine-trees in their in- 
vading masses of sand. 

The most favorable days for observing the progressive march of dunes 
are those Avhen a gentle breeze, strong enough, however, to drive the sand 
before it, blows in a perfectly uniform manner. From the top of the dune 
we see innumerable grains of dust swiftly scaling the slope. Glittering in 
the sun, and whirling like the midges in a fine summer's evening, they at- 
tain the summit, then accumulate in the form of a coi'nice on the other 
side of the ridge, and from time to time occur little falls, which spread 
over the surface of the talus, like sheets of water over the sides of a rock, 
and whose contours remind one of light draperies covering one another. 
When a high wind blows with violence, and in successive gusts, the en- 
croachments of the dune are accomplished in a manner much more rapid, 
but often much more difficult to observe. The summits of the hillocks, 
which are enveloped in clouds of dust, resemble volcanoes vomiting smoke ; 
the front of the dune is furrowed and scooped out by the ^ind ; masses 
of sand, laden with marine remains brought by the storm, fall down with 
an audible sound, and are disposed in unequal layers over the descending 
talus. A section taken across a dune would permit us to count and meas- 
ure the difierent strata, varying in thickness and composition, which the 
winds have successively brought. Here we find a fine sand-like dust; 
there, a stronger wind was charged with a heavy shelly sand; while, 
again, a storm has carried away entire shells, branches, and waifs. How- 
ever, the particles transported by the wind are, in general, all the finer the 
farther they M'e from the sea, and this is reasonable, for they must fly 




Fig. 91 Section of a Dune. 

more easily the less resistance they ofier to the aerial current which bears 
them. In the narrow rows of dunes which border certain parts of the 
coast of the Mediterranean, we can clearly see, over a breadth of some 
hundreds of yards, the moving materials succeed each other, distributed 
according to their weight. First, there are the fragments of shells, then 
the large arenaceous debris, then the fine sands.* 

* Marcel de Serres, Bulletin de la Societe Geologique de France, 1859. 



192 THE OCEAN. 

If the inclined plane which the dune turns toward the sea remained per- 
fectly even, the zone of the shore would only present, in all its extent, a 
single rampart of sand gradually encroaching on the lands. But at length 
the slope of each dune can not fail to offer some inequalities caused Tby for- 
eign bodies, or by plants that take their origin in the sand. All the salient 
points strong enough to resist the wind serve as supports to new dunes, 
grafted, so to say, on the sides of the ancient one. These new dunes them- 
selves bristle with irregularities, which other sand-hillocks soon cover, and 
it is thus that all those ranges of moving hills arise, which are separated 
by long and narrow valleys, called lettes or IMes by the peasants of the 
French Landes. In certain places, especially between Biscarosse and La 
Teste, these " lettes," for a length of several leagues, i-esemble the dried-up 
beds of large rivers, surrounding large islets of verdure with their sandy 
waves. 

Notwithstanding the ajsparent disorder of these hillocks, in the midst 
of which an inexperienced traveler might easily lose his way, the general 
disjDosition of the sands can always be referred to a uniform type, which 
local geographical facts variously modify, such as the contours of the ma- 
rine shore, the nature of the soil, the force and direction of the winds, the 
presence or absence of vegetation. The dune nearest to the sea, and, in 
consequence, the most recent, is less elevated than the older hillock situ- 
ated immediately beyond ; and this, in the same way, attains a less con- 
siderable height than the following hill. In a system of dunes, generally 
each range which is developed fafther inland exceeds the preceding ones 
in elevation, and forms, as it were, a new step on the slope of the great 
primitive dune which serves as an avant garde to the army of sands. 
This last dune, the true crest of the entire system, enlarges itself, little by 
little, with all the materials which have served for the formation of the 
inferior dunes situated on the side nearest to the sea. The grain of sand 
which the air carries to the summit of the first hillock, and which falls 
afterward into a ravine, may remain during centuries under the super- 
incumbent masses ; but owing to the constant progress of the dune, the 
superficial layers of which are swept by the wind and then let fall by it 
farther down the talus, this grain of sand at last re-appears, is carried 
anew to a summit, it descends again, and thus does not cease to travel 
from dune to dune to the last. 

As the innumerable arenaceous particles are moved by virtue of rigor- 
ous laws, we can consequently measure the force of the winds, by the 
height of the mass, and the rapidity of the displacement of the hillocks. 
Attentive observation permits us, in the same way, to compare with each 
other the various atmospheric currents which drive the sands onward, 
and to indicate exactly the one whose action is the most energetic. 
Thus, in the peninsula of Arvert or La Tremblade, situated between the 
mouth of the Gironde and that of the Seudre, the chain of dunes rises 
gradually in a northerly direction, and it is at the northern extremity 
that the highest hillock is found. This phenomenon is explained by the 



I'lif Ocoan.A-c 



THE DUNES OF LA TESTE 



P[..X1 



W t tl^iz 



Z^^tZ 







Engraved by Erliaj'd 



«> »4 * ^ / 



CRESVENT-SHAPEB DUNES. 



193 



frequency and intensity of the south-west wind which blows in these 
parts ; in virtue of " the parallelogram of forces," it carries the sand far- 
ther and higher than the winds from the west and north-west can. 

Every issolated dune assumes clearly -defined contours, resembling 
those of a crescent. It is easily understood why the hill must advance 
in such a manner as to project a curved point on each side of its principal 
mass. The grains of sand which the wind causes to ascend the height 
of the central part of the dune have to describe a longer path and to 
slide farther down the counter-slope than the particles of the two lateral 
extremities. They proceed consequently with less speed ; the ends, ex- 
ceeding in rapidity the rest of the dune, bend forward, in the shape of 
advanced horns, and give the whole of the moving hill the aspect of a 
volcano whose crater has fallen in. That which contributes still more to 
cause these sandy hillocks to assume this semicircular form is, that the 



Mayan ^ I': 




-iZ-:^..,, -^^ 



Fig. 92.— Crescent-shaped Dunes. 
13 



194 THE OCEAN. 

prevailing wind does not always blow perpendicularly to the mass of 
the dune. Its direction is often oblique ; now in one direction, and now 
in the other. It then makes the wings of the dune, the crest of which 
it strikes at right angles, advance more rapidly. 

In the Desert of Atacama, the Pampas of Tamarugal, in the plains of 
Texas, in the Sahara of Algiers, in the Nubian deserts, and in almost all 
the regions traversed by shifting sands, the crescent-shaped dunes pre- 
sent such a regularity of form that all travelers have been struck by it.* 
The Landes of Gascony also offer remarkable examples of this semicircu- 
lar arrangement of the crest of the dunes. In the environs of Arcachon 
and La Teste all these hillocks have the appearance of fallen-in volcanoes, 
and are distinguished by the rich vegetation of broom and bushes which 
fill their craters or crouhots. In those parts of the coast of the Landes 
where the crater-shaped form of the dunes is obliterated, it is evidently 
because two or more hillocks have been united and, so to say, amalgama- 
ted by the impetuous wind which blows from the sea. However, we can 
account to ourselves for all these phenomena by studying the little swell- 
ings of sand, or miniMure dunes, which are formed in thousands on the 
marine shores. 

* Poeppig, Meyen, Bollaert, Gillis, Laurent, Georges Pouchet. 



HEIGHT OF SAND-HILLS. 195 



CHAPTER XXIV. 

HEIGHT OF THE HILLOCKS. — ADVANCE OF THE DUNES. — DISPLACEMENT OF 
"eTANGS." — DISAPPEARANCE OF VILLAGES. 

In Europe the highest hillocks of sand are found on the coast-line of 
the Netherlands, on the Atlantic coasts of France, and in Scotland on the 
shores of the Firth of Tay. As to the dunes of the Mediterranean, they 
are generally lower than those on the coast of the ocean. The gulfs of 
the south of Europe having a hardly perceptible tide, their sandy shores 
are not incessantly displaced, like those on the strands of the ocean, and 
consequently they are less exposed to the winds which drive before them 
the finest particles. It is to the north of Africa, round the gulfs of the 
Syrtes, where the ebb and flow have the greatest development, and where 
sandy beaches occupy vast tracts, that the Mediterranean dunes attain the 
most considerable height. In France, those that are seen from Port Ven- 
dres to the mouths of the Rhone, hardly rise to more than eighteen or 
twenty-one feet in height, because the banks on which these hillocks are 
formed have not a sufficient breadth, and, above all, because the prevailing 
wind, the mistral, blows from the north-west, and carries the sand from 
the Hangs into the Mediterranean, 

On the coast of the Landes of Gascony, where the waves of the sea 
bring six millions of cubic ya<3.s of sand each year,* a great many dunes 
exceed the elevation of two hundred and twenty-five feet. There is even 
one, that of Lascours, whose long ridge, parallel to the sea-shore, attains 
two hundred and sixty-one feet in several places, and raises its culminating 
dome to a height of two hundred and ninety-one feet. It is true that 
this height seems to mark, in France, the extreme limit of the ascent of 
the sand, for the ranges of dunes situated to the east of the dune of Las- 
cours are far less elevated. One Avould be tempted to admit that, after 
having arrived at this great height, the lower strata of wind from the 
west, compressed by the more elevated masses of air, h^ve not the nec- 
essary power to cause the particles of sand to mount again, and are 
obliged to descend toward the plains of the interior, taking the crests 
from the hills previously formed. In Africa, on the low shores where the 
ocean bathes the great Desert of Sahara, the enormous quantity of sandy 
materials that the eastern winds bring from the desert, and which the 
west wind drives back to the interior, permit, it is said, the dunes of Cape 
Bojador and Cape Verd to attain an elevation of from three hundred and 
ninety to nearly six hundred feet.f 

The highest dune in the New World is perhaps that of Morro-Melancia, 

* Laval, Annates des Ponts-et-Chausees, 1842. 
t Carl Ritter, Afrika. 



196 THE OCEAN. 

near Cape St. Roch, nearly one hundred and fifty feet high ; it rests on 
one side against a wooded hillock. 

To the eyes of a traveler accustomed to the ascent of the Alps and the 
Pyrenees, these are very humble summits ; yet these heights of sand as- 
sume the asjDect of actual mountains, and their chains, arranged parallel 
to the shore, like ranges of enormous waves, seem to constitute an entire 
orographical system. Their bold taluses, their solid ridges, cut as with a 
chisel, the regular form of their tops, the general harmony of their con- 
tours, unceasingly varied at the will of the wind, give them an astonish- 
ing appearance of grandeur. The very even base-line which the sea- 
shore presents likewise aids to the illusion by contrast, and contributes 
to the grand aspect of these white hills. The old name, at once Celtic 
and Latin, of the dunes (dun), which was applied to mountains and steep 
hills, and which we still find in the names of several towns — Verdun, 
Loudun, Issoudun, Saverdun, proves that our ancestors had been singu- 
larly struck with the bold form of the sandy hillocks of the coast. 

While gaining incessantly on the plains of the interior, the dune buries, 
without destroying, all solid objects, stones, rocks, trunks of trees, or hu- 
man dwellings. Sometimes even it entirely covers pools of water, and 
causes them to disappear for some time under its sloping talus. When 
the sand brought by the wind falls regularly on a sheet of water, stag- 
nant or covered with scum, it often forms a fine layer, completely veiling 
the water which bears it, from view. This bed can become solid enough 
to remain in equilibrium even when the level of the sea falls below it, and 
soon the particles of sand, dried by the solar rays, no longer betray the 
existence of the hidden pitfall. The herdsjuan or animals which set foot 
on the surface of the blouse are suddenly ingulfed more or less deeply, 
and the waters of the pool rise around them. Most frequently they es- 
cape with the fright. Little by little the crumbling sand is heaped up ; 
they allow the bottom to be consolidated, then quietly raising one leg, 
they wait till a sort of step is formed, and thus mount from stair to stair. 

If little pools are sometimes apparently swallowed, the more consider- 
able masses of water, situated at the base of the dunes, are continually 
driven back into the interior. The rivers, arrested in their course and 
changed into ngarshes, are also forced to retreat, and mix their waters 
with those of the pools. This formation of lakes and marshes, parallel to 
that of the dunes, is one of the most remarkable features of the coast-line 
-of the French Landes. A row of ponds, difiering in form and size, but all 
situated at a nearly equal distance from the sea, is prolonged over a space 
of one hundred and twenty-five miles. One large bay, the basin of Arca- 
chon, has been able to maintain a wide communication with the ocean, 
owing perhaps to the river which it receives from the interior. But all 
the other sheets of water, to the north the etangs of Hourtin and Lacanau, 
and to the south those of Cazau, Parentis, Aureilhan, St. Julien, Leon, 
and Soustons, only communicate with the sea by tortuous and rapid 
streams, and are now at a level considerably higher than that of the sea. 



ETANO OF CAZAU. 



19Y 



Tlio etang of Cazau, the most elevated of all, and that which has been 
driven gradually inland by the strongest dunes, spreads its sheet of wa- 
ter at an altitude varying from sixty-three to sixty-six feet, according to 




Fig. 93 " Etangs," or Littoral Lakes of Cazau, Parentis, aud Aureiltian. 

the seasons. It has not less than 14,826 acres of mean superficies. The 
spectator who contemplates it from the top of a hillock would think he 



198 THE OCEAN. 

saw a vast marine bay, for a great part of the opposite shores escape the 
eye, and the isolated trees, which mark afar off the distant bank, resemble 
a fleet of ships at anchor in a road ; the white boulders of sand, of a trian- 
gular form, which are perceived at the foot of the green dunes, and which 
appear like so many sails of ships skimming along the coast, increase the 
illusion. Nevertheless, it is probable that the etang of Cazau was former- 
ly a gulf of the ocean, for the bottom of this small inland sea is still found 
to be thirty-six feet below the marine level. The fishermen, who are the 
best authorities in such matters, uniformly attest that, in the lowest pai'ts 
of the pond, the lead touches the sand at fifteen fathoms. They also as- 
sert that it formerly communicated by deep trenches with the sea, and 
they even indicate the bay of Maubrucq as having been the ancient port, 
and trace the direction followed by the channel in the middle of the 
dunes. In the same way, the fishermen of the etang of Hourtin still show 
the site of the old port of Anchise. 

It is easy to explain the gradual transformation of the ancient Gulf of 
Cazau, and other marine bays which indented the now uniform coast of 
the Landes. Separated from the ocean at first by a slender ridge of sand, 
as is often formed on low beaches, these bays, which are changed into 
ponds, have been gradually driven inland by the parallel rows of dunes. 
Under the enormous pressure of the sand they have climbed, so to say, 
the slope of the continent. At the same time, the rains and rivulets, ar- 



J 



Fig. 94— Formation of "Etangs.' 



rested in their course, have incessantly brought their contribution of fresh- 
water to the new lakes, while the salt-water retreated gradually, by natu- 
ral channels, between the hillocks. Thus the grains of sand which the 
wind drives before it have sufiiced, in the course of centuries, to change 
gulfs of salt-water into ponds of fresh-water, and carry them into the in- 
terior of the continent, to a height considerably above the Atlantic. 

The same phenomena occur also in the sandy islands which are found 
in the middle of the sea. The greater part of these islands have a per- 
fectly regular form, due at the same time to the currents which bathe 
them, and to the winds which form the dunes. In the centre of the trian- 
gular or crescent-shaped space which they surround with their moving hil- 
locks, they inclose one or several ponds, which formerly were a part of 
the sea, and which have transformed themselves by degrees into pools of 
saltish and finally fresh-water. In Sable Island, situated not far from the 
mouth of the St. Lawrence, we can observe this phenomenon of transition 
actually in progress. While the large lagune of the interior, too exten- 
sive to be rapidly purified, is still filled with salt-water, the small ponds 
lying between the dunes are already fresh-water. 

Numerous have been the disasters occasioned by the invasion of dunes 



DISASTERS CAUSED BY DUNES. 



199 



or pouds during the historic era. The villages situated at the eastern 
base of the dunes of Gascony, on the shores of the ponds, must be moved 




Fig. 95. — Isle Thelenji, iu the Caspian Sea. 



from time to time toward the east, for fear that they should be swallowed 
by the sands or the waters. At the approach of the danger the threat- 
ened inhabitants sometimes attempted a vain resistance. As soon as an 




Fig. 96.— Sable Island. 



east wind succeeded to the regular winds froi:H||yie Avest, herdsmen and 
laborers, armed with spades and pick-axes, repaired in all haste to the to]) 



200 THE OCEAK 

of the dunes, and, filled with a purposeless ardor, they destroyed the crest 
of sand, and delivered it to the power of the wind. But the regular winds 
soon brought back the sand again, the dunes recommenced their advance, 
and routed the army of peasants. For fear of being buried, Ihey were 
obliged to destroy their huts, in order to carry away the materials and 
build new dwellings at a certain distance inland. Years and centuries 
passed ; but the dunes and the ponds constantly advanced, and the in- 
habitants were again condemned to transport their villages into the midst 
of the heaths. These were foreseen misfortunes, and the chronicle pre- 
serves silence as to the successive emigrations ; it confines itself to men- 
tioning the names of some churches which were obliged to be abandoned 
to the sands and reconstructed far on the plateau of the Landes. Thus 
we know that the church of Lege was rebuilt in 1480 and in 1650, the 
first time at two and one-eighth miles, the second at nearly two miles far- 
ther inland ; but the halting-places of other local monuments of the same 
district are not known in an exact manner. As to the now vanished 
towns of Lislan, Lelos, and many others, their ancient situation is un- 
known. After having lost its port and its hamlets, the township of Mim- 
izan, formerly very important, was about to be entirely buried, when, at 
the last moment, they succeeded in fixing the dunes by palisades and 
plantations. The semicircle of invading hills, like the serrated mouth of 
a crater, still seems to be on the point of devouring the houses. 

Dunes have often been compared to gigantic sand-glasses measuring 
time by the progressive march of their sandy talus. The comparison is 
just, for the western winds, which efiect all the changes on the coast-line 
of the Landes, obey at present the same laws as they did thousands of 
years ago, and very probably their force has not changed during that in- 
terval of time. The dunes, the ponds, and even the villages on the shores, 
may thus be considered as real geological chronometers ; but, unfortunate- 
ly, the indications that they furnish have not yet been deciphered with 
any certainty, and now that the dunes are fixed, it is too late to under- 
take this study. The illustrious Breraontier (whose book, printed in the 
year 1V97,* is still an authority on the question of moving sands) collect- 
ed during eight years a series of observations which have given an aver- 
age of from twenty-two to twenty-seven yards for the annual progress of 
the dunes of La Teste. This result agrees in a remarkable manner with 
the indications furnished by the enci-oachments of the dunes of L6ge dur- 
ing the last four hundred years. In admitting as normal the average cal- 
culated by Bremontier, one would arrive at this conclusion — that in the 
lapse of twenty centuries the dune would be able to invade the entire dis- 
trict of the Landes and cover the town of Bordeaux. A thousand years 
would even have sufiiced to transform the fair plains of Bordelais into 
marshes, for the Hangs constantly driven back by the invading dunes, 
would have spread on the eastern side after having passed the culmina- 
ting line of the plateau|^ the Landes. Researches undertaken in other 

* Memoire sur les Dunes. 



OBSERVATIONS NECESSARY. 201 

places would have doubtless confirmed the observations made by Bre- 
montier ; but in the absence of these, we can not accej^t measures taken 
at the foot of a group of isolated dunes as applying to the host of sands 
from Bayonne to the Point de Grave. ' In order to pronounce definitely, 
we must wait for observations which will not fail to be made one day, on 
the advance of the dunes in all those parts of the globe where these hil- 
locks have not yet been arrested. 



202 THE OCEAN. 



CHAPTER XXV. 

OBSTACLES OPPOSED BY NATUKE TO THE PEOGEESS OF DUNES. — FIXATION 
OP THE SANDS BY SEEDS. 

The work of nature is, however, double ; and if on one side she has- 
tens the advance of the sands, on the other she attempts to arrest them. 
She herself points out the means of prevention, or else prevents spontane- 
ously the disasters of which she is the cause. In certain places, and es- 
pecially on a part of the coasts of the Landes, she exercises a physical 
and chemical action by employing the oxide of iron which the water con- 
tains to consolidate the sands and transform them gradually into actual 
rocks. Elsewhere organic cements, composed of broken shells and re- 
mains of silicious and calcareous infusoria, agglutinate the arenaceous 
particles, and give them the necessary stability to resist the winds. But 
these means of consolidating the sands are exceptional. It is principally 
vegetation which fixes the moving hills on the sea-shore. On almost all 
coasts the sandy and calcareous debris of the soil contain enough fertiliz- 
ing principles to nourish a certain number of hardy plants, which do not 
fear the salt air of the sea, and which send down their roots to a great 
depth, so as to absorb the necessary moisture. Among these hardy veg- 
etables the commonest, and most useful at the same time, is Marram-grass 
[Arimclo are7iaria), whose slender and flexible stems can hardly arrest 
the wind, but whose strong roots, sometimes twelve or fifteen yards long, 
develop all the better the less consistence the sand has. Various species 
of convolyuli creep over the ground, and fixing their vigorous cordage 
from place to place, sometimes envelop an entire dune in their net- work of 
leaves and flowers. Other plants rise more proudly, but if their stem is 
buried in the sands they transform it into a root, and give birth to a new 
shoot, which may be interred in its turn, without the plant being in dan- 
ger of perishing. Thus such a seed germinating at the base of the dune 
often produces a' plant which ends by spreading to the summit of the 
mountain, and fastens by a cable of roots the arenaceous strata which the 
creepers of the convolvulus fix on the surface. A number of plants, 
whose frail stems are half buried in the sand, are perhaps contemporary 
with the dune itself;* perhaps even they existed before mankind had a 
history. 

In this strife between the force of the winds and the power of vegeta- 
tion, the definite issue depends, at the same time, on the cHmatological 
conditions, the nature of the soil, the form of the shore, and various other 
. circumstances, among which we must rank, in the first place, the havoc 
caused by men and animals. In South America, on the shores of thos.e 
* Aug. Pyr. de Candolle ; Elie de Beaumont. 



FORESTS ROWING ON DUNES. 203 

tropical countries where the development of plants is favored, according 
to the seasons, by an extreme heat and by torrents of rain, and where the 
sands contain a considerable proportion of animal and vegetable remains, 
most of the dunes are already fixed at a few yards from the sea by mimo- 
sas, cactuses, and thorny trees. However, on the eastern shores of all the 
rivers of equatorial Brazil, which discharge themselves near the mouths 
of the Amazons, we see, even somewhat far from the sea, ranges of dunes 
from twenty-live to fifty feet in height, which move incessantly, driven 
by the breezes of the trade-winds.* This mobility of the sands is undoubt- 
edly connected with this fact, established beyond question by Coutinho 
and Agassiz, that the shores are depressed in that" part of Brazil, and, con- 
sequently, t^ey incessantly change their form, so that the dunes have not 
yet had time to be fixed. 

In Europe the flora of the sands is less rich than in equatorial countries. 
On the coasts of Jutland it is composed of only two hundred and thir- 
ty-four species of plants, very insignificant for the most part,f and the 
" white " dunes of the Danish peninsula, as well as those of Gascony and 
Holland, have also not enough cohesion to resist the furious western 
winds which assail them. It is probable, nevertheless, that even in the 
countries of the temperate zone the modest herbaceous vegetation of the 
sands of the coast could, after a certain lapse of centuries, acquire the 
strength necessary to fix the dunes, and prepare, by the slow accumu- 
lation of its remains, a vegetable bed, where large trees would grow 
spontaneously. 

If it were not so, it would be diflicult to understand how all the dunes 
of Europe were originally covered with forests. According to the unani- 
mous testimony of the ancient. geographers, the woods extended to the 
sea-shore in those plains which are now the Netherlands, and the Bata- 
vians, the Angles, and the Frisons had no special word in their idioms 
Avhich designated a hillock of moving sand.J Neither the great geogra- 
pher Strabo, nor Pliny, the encyclopaedist, nor any other writer of antiq- 
uity, mentions the existence of hills driven by the wind, though this phe- 
nomenon was certainly of a nature to strike them. Under a great many 
of the dunes of Gascony trunks of oak and pine trees, with other sub- 
stances, are discovered buried in the sand, above the ancient level of the 
Landes. Moreover, some dunes still bear magnificent woods, which can 
count at least several centuries of existence, and which probably were not 
planted by man. Not far from Arcachon one may wander in a forest 
where gigantic pines rise, nnrivaled in France, and oaks forty-six feet in 
circumference. Title-deeds of 1332 speak also of forests which covered 
the dunes of Medoc, and where the seigneurs of Lesparre went in merry 
company to chase the stag, the boar, or the roebuck. Montaigne,§ too, 
writing in the middle of the sixteenth century, says that invasions of the 
sand had taken place " for some time." Besides, why should the Landese, 

* Revue Maritime et Coloniale, 1866. t Andresen, Om Klitformationen ; Mai'sh. 

X Staring, Voormals en Thans ; Marsh. § Essais, livre iv. 



204 THE OCEAN. 

like the Sjoaniards, give the name of monts or montag7ies to their forests, 
even those of the plains, if not because their hills of sand were, in former 
times, uniformly covered vs'ith trees ? 

Unhappily, all those fine forests which once protected the low lands of 
the «ea-coast against the invasion of the sands were successively destroyed 
during the evil days of the Middle Ages, either by barbai-ian invaders, or 
by improvident lords, or by the peasants themselves. Even in the last 
century the King of Prussia, Frederick William I., being in gi*eat want of 
money, caused the forest of pines to be cut down, which extended with- 
out interruption over the dunes of the Frische Nehrung from Dantzic to 
Pillau. The operation brought him the sum of 200,000 crowns, but the 
moving sands invaded the great inland bay, destroyed the #sheries, ob- 
structed the navigable channel, buried the defending fortresses, and mod- 
ified in the most vexatious manner the hydrographic economy of all those 
parts.* In Holland and in Biittany this dismantling of the coast has pro- 
duced still more fatal results. On the borders of Lake Michigan, and at 
Cape Cod (Massachusetts), the clearing of the shore has also produced the 
formation of moving hills.f But the inhabitants have only themselves to 
complain of; the dunes are their work. A single imprudence may cause 
great misfortunes; and thus, according to Staring, one of the highest 
dunes of Friesland owes its origin to the destruction of a single oak, J « 

It is for man now to arrest by his labor those hillocks of sand which he 
has, so to say, created by his imprudence. Happily this is not an impos- 
sible task. The shepherd of the French Landes, when he wishes to pro- 
tect his cabin, erected in the depth of some ravine of the dunes, takes care 
to cut, in the ledes and surrounding marshes, grass or rushes, which he 
spreads over the soil in such a manner as to cover it completely, and to 
leave none exposed to the sea-breezes. This is sufiicient; the sand re- 
mains immovable, and the dune is fixed for the future ; so long at least 
as no horse's foot, or the teeth of a sheep or wild animal, a shower of rain, 
or any other cause, have penetrated the protecting layer and restored 
their mobility to the sands. It is then necessary to carj)et the ground 
with a new litter of plants. 

This means of protection, which is moreover only practicable over small 
'extents, is evidently quite provisional ; to obtain a definite result we must 
have recourse to the direct fixation of the dunes by the seeds of trees or 
other plants, so as to present an insurmountable barrier to the winds. In 
modern times the Dutch, those great masters for all works concerning the 
sea and the coasts, have been the first to recognize the absolute necessity 
of arresting the dunes. Defended and menaced at the same time by those 
masses of moving sand which never cease to encroach on their territory, 
even while protecting it against the assaults of the sea, they have under- 
stood that the very safety of their country may depend on this rampart 

, * Foss, Zeitschrift fur die Erdkunde, 1861. 

t Marsh, Man and Nature. 
% De Bodem van Nederland, tome i., p. 425. 



FIXATION OF MOVING SANDS. 205 

of hills, and for a century thoj^ have effectually consolidated it by plant- 
ing reeds, maples, and firs. 

The first attempts at the fixation of the dunes made in Gascony date 
from tlie beginning of the eighteenth century. M. de Ruhat, who had ac- 
<piired the ancient Captalate de Buch, sowed some of the hills of La Teste 
with pine-trees ; but though this plantation succeeded perfectly, the work 
was not continued, and everywhere else the indolent Landese allowed the 
dunes to advance to the assault of their villages. Later, the brothers 
Desbiey and the engineer Villers proposed repeatedly, at various times, 
the fixation of the entire district of sands. Their voices were not heard. 
It is to the celebrated Bremontier that the honor is due of first causing 
to be adopted and put in practice a complete plan for the culture of all 
the dunes, Lispired with the writings and example of his predecessors, 
and not disdaining to interrogate the herdsmen, who knew by tradition 
the means of arresting the sands, Bremontier first applied himself to the 
task in 1787. The works were interrupted in 1789, resumed in 1791, and 
completely abandoned again in 179'3, in consequence of the opposition giv- 
en by several of the inhabitants of La Teste, But important results had 
been already obtained. More than six hundred and twenty acres of mov- 
ing sands had been fixed in the environs, of Arcachon ; pines, oaks, and 
vines were in perfect growth, and the sowing of every two acres had not 
cost more than two hundred francs. The possibility of arresting the ad- 
vance of the dunes at little cost was perfectly demonstrated. 

At the commencement of, this century the interrupted work was re- 
sumed, and it was comjjleted some years ago. The dunes of Gascony, 
fixed for the future, enrich the countries which they formerly threatened 
to buiy, and in consequence of the increasing value of the pines and their 
productions, we must reckon the annual increase of public wealth on the 
coast at hundreds of thousands of francs. The estimated present value 
of the forests of the Landese dunes is twenty-five millions; that is to say, 
six hundred francs the acre. Thus, the means of safety ajaplied by Bre- 
montier has become a cause of prosperity to the inhabitants. At the 
same time, several happy results, which could not be looked for at first, 
have been obtained. The sand, protected from the rays of the sun by the 
shade of the pines, produces herbs which are utilized as straw or food for 
cattle. The marshes, which during six months of the year were trans- 
formed by rain-water into impenetrable morasses, have been drained with- 
out the intervention of man, owing to the thousands of roots constantly 
pumping up the moisture from the sands. The surface of the vast ponds 
situated at the eastern foot of the dunes is lowered likewise, to furnish 
the forest-trees with the water necessary for their growth. Besides this, 
the fixation of the dunes has caused the "blouses" to disappear, -in which 
men and animals were ingulfed ; the sands do not advance any farther, 
and the pools have ceased to exist. Science has repaired the disorders 
formerly caused by man's imprudence. 



PAET II.-THE ATMOSPHERE AND 

METEOROLOGY. 



BOOK I— THE AIR AND WINDS. 



CHAPTER I. 

AIR THE AGENT OF THE VITAL CIRCULATION OP THE PLANET. — PHENOMENA 
OF EEFLECTION AND EEPRACTION. — MIRAGE. 

Death and eternal silence would reign over all the earth if it were de- 
■ prived of the atmosphere that envelops our planet. This gaseous, trans- 
parent, and invisible mass, which scarcely seems to form a part of the 
earth, is nevertheless its principal element; for it is the most mobile, 
and it is by its agency that life is sustained. The earth supports us, but 
whether men, animals, or plants, we alike require the air for our existence. 
Although not flying in it like birds, all living beings, whether they walk, 
climb, or fix their roots in the soil, are not the less children of the atmos- 
phere. 

Considered as one of the heavenly bodies, our planet is compo^d of a 
solid kernel surrounded by two fluid strata. The kernel is that which 
bears more especially the name of the earth, it is the rocky beds contain- 
ing lava, molten metals, and the entire mass of unknown substances which 
occupies the centre of the globe. The sheet of water forming the seas 
and the net-work of rivers covers this solid skeleton, and above this wa- 
tery envelope is stretched a second spherical layer still more fluid, and 
whose currents and counter-currents incessantly circulate from the pole 
to the equator, and from the equator to the pole, with the regularity of 
the lungs of man, by turns filled and exhausted. The atmosphere is truly 
the breath of the planet ; like its satellite, which most astronomers tell us 
is destitute of a gaseous envelope, the earth would be only a dead star 
rolling in space if it suddenly lost the stratum of air that surrounds it, and 
ceased to respire the regular breath of the winds. 

The subtle and transparent air is composed of the same gases which are 
found in greater abundance in the opaque and solid crust of our globe. 
The four principal elements of all vegetable or animal organism — oxygen, 
nitrogen, hydrogen, and carbon — are found likewise in the atmosphere: 
the first two as constituent elements of the air, the third united with 

oxygen under the form of watery vapor, and the fourth mixed with the 

t 



COMPOSITION OF THE AIR. 20 "7 

breath expired by animals, and with many other gases resulting from the 
decomposition of organic matter. Between the action of nature and the 
eternal movement of the atmosphere an exchange is constantly being ef- 
fected, by which the gases, one instant in the animal, plant, or rock, fixed 
in an or<2;anisra or in the terrestrial strata, are disengaged and recorapose 
the atmosphere. 

Animals and plants would soon be all destroyed, for want of necessary 
aliment, if the mixture of vapors and gas were not effected by the inces- 
sant movement of the aerial masses. Men and animals would gradually 
kill themselves by absorbing again the carbonic acid already expeljed 
from their lungs ; and plants plunged in an atmosphere too full of oxygen 
emanating from their leaves would end too by dying. Happily, the cur- 
rents of air, which pass in immense spirals over the surface of the earth, 
uniformly mix all the gases they carry away with them, and thus favor 
life over their whole course. To the temperate regions, which are princi- 
pally the domain of man, they bring the oxygen which the immense for- 
ests of the tropical zone have exhaled ; to these same forests they impart 
the carbon which is life to trees, and would be the death of man. Still 
more, they animate the globe itself, by carrying immense quantities of va- 
por to the mountains where the net-work of springs is elaborated, and in 
causing to circulate above the sea a dry air eager to absorb the water 
which evaporates from its surface. Like the heart in living organisms, 
the productive zone of the atmospheric currents occupies the central region 
in the ocean of air, and moves alternately to the north and south. It is 
thus that a movement of systole and diastole is produced in all the aerial 
mass, impressing the initiatory speed to the arterial currents which carry 
fertility to all points of the planet. 

Every particle of gas passes thus continually from life to life, and es- 
capes from death to death ; by turns, wind, wave, earth, animal, or flower, 
despite its smallnesa, is the symbol of infinite raotio% The air is an inex- 
haustible source whence all that lives draws its existence, an immense 
reservoir into which all th^t dies pours its last breath. Under the action 
of the atmosphere all the scattered organisms are born and perish. Life 
and death are equally in the air which we breathe, and perpetually suc- 
ceed one another by the exchange of gaseous particles. The same ele- 
ments which are exhaled from the leaves of the tree are carried by the 
wind to the infant that is just born; the last breath of a dying man goes 
to form the brilliant corolla of the flower, and compose its penetrating 
perfume. The breeze which gently caresses the stems of the plants is 
farther on transformed into a tempest, uproots large trees, and destroys 
ships, with all their crews. It is thus, by an infinite series of minor catas- 
trophes, that the atmosphere sustains the universal life of the globe. 

Comparable to the ocean, as to the incessant circuit of its waves, the 
great atmospheric sea is not, however, inclosed in a basin bounded on all 
sides. The atmosphere travels without cessation, bearing away on its 
wings all the light objects which are exposed to its cuiTcnts. It takes 



208 THE ATMOSPHERE AND METEOROLOGY. 

up tfce ashes from a crater in eruption, and lets them fall in places often 
hundreds of miles distant ; it raises in its eddies myriads of animalculse or 
clouds of pollen, which are wafted by it across seas to fall again in impal- 
pable dust. It carries the sea itself in the form of clouds, and distributes 
it as rain and dews over the continents ; it becomes highly charged with 
electricity, and discharges itself by the rays of the aurors borealis, or by 
vivid lightnings. It is the great vehicle by means of which the universal 
interchange of the elements which compose the solid crust, the mass of 
waters, and of organic beings, is accomplished. 

t' The world is small !" said Columbus ; but it is principally owing to 
the air, which disregards distances, that the earth is diminished. What- 
ever be the number of yards or miles traversed by a seed, the point where 
it falls is not distant from the mother-plant. The northern coasts of the 
Mediterranean are brought nearer the great deserts of Africa, dust of 
which is brought by the sirocco ; and in the same way we may say that 
the shores of Brazil, toward which the trade-winds blow, are contiguous 
to the distant archipelagoes of the Azores and the Canaries. All those 
parts of the world united by atmospheric currents become thereby neigh- 
bors to each other, if not for the creatures who walk on the ground, at 
least for those which are carried by the movements of the air. By the 
incessant mixture of the aerial masses all the regions of the solid kernel 
of the earth are brought nearer, contrasts are blended, and harmony is 
established between the productions and the climates, no less than in the 
general aspect of nature. 

The winds are also powerful geological agents. Thus the aerial cur- 
rents of certain latitudes transport clouds of dust, which may at length 
render vast countries sterile or fertile, either by covering the natural soil 
with an unfruitful' layer, or by effecting a hai^py mixture with it. On the 
banks of the Nile, the sand of the desert, which the wind mingles Avith 
the thick mud of tl|e river, contributes to develop the marvelous pro- 
ductive force of the land, while in» the neighboring plains, which are des- 
titute of rroisture, it- buries the plants and renders the soil wholly unfit 
for vegetation. Elsewhere, and principally on the low coasts of the 
sea, the wind drives hills of sand across the plains, barring the outlets 
of the streams, and gradually driving the water up the slope of the con- 
tinent.* 

In certain places the aerial current even goes so far as to temporarily 
change the level of the sea ; it sometimes arrests the waves, or hurls them 
against the shores, and alternately dries up the bed, and causes disastrous 
inundations. Sometimes the wind, which descends with violence from 
the polar regions of Norljh America to the Gulf of Mexico, keeps back 
three or even four successive tides. Then these, returning altogether in 
one foaming mass, sweep over whole islands off the low coasts of Louisi- 
ana and Texas. In the same way, when the pampero or south-west wind 
blows over the great estuarj?- of La Plata, its waters are sometimes low- 

* See above, p, 198. 



WORK PERFORMED BY THE WINDS. 209 

ered by twelve or even Eighteen feet in less than half a day, and the ves- 
sels that were floating in the roadla'eniain stranded in the mud,* 

This is not all. The wind can also modify the configuration of the 
shores, since the waves of the sea, which •contribste so largely toward 
the sculpturing of them, receive from it their impulsive force. Thus the 
large arm of tha Rhone perhaps owes its south-easterly direction to the 
mistral which descends from the Cevennes.f 

As to the delta of the Mississippi, its exterior contours are probably 
modeled by the south-east monso'f>n which prevails in that country ; the 
southern passage, which opens exactly in the direction of the prevailing 
wind, is almost entirely obstructed by the dike of mud that the surf has 
raised across its current. The two arms of the Mississippi which carry 
the gpeatest quantity of water are directed, the one to the south-west, the 
other to the north-east ; that is to say, each of them forms a right angle 
with the monsoon from the south-east. It is the aerial current which has 
forced the long peninsulas of the Mississippi to spread thus over the wa- 
ters like the branches of a great fallen tree, J 

The geological labors of the winds are, however, accomplished, for the 
most part, in an indirect manner, either by the evaporation of the moist- 
ure of the continents, or by causing considerable downfalls of rain. Dur- 
ing the course of ages the contours of the land and sea have not ceased to 
change, and, in consequence of these gradual modifications, thdfrwinds 
themselves have been subjected to analogous variations. Some are satu- 
rated with the vapor of water, and the clouds that they carry are depos- 
ited in rivers and lakes in the midst of land. Other atmospheric cur- 
rents have lost their moisture in great part, and then, in passing over in- 
land seas, they have absorbed them — pumped them, so to sjjeak, leaving 
behind them smiling plains transformed into deserts. Without any doubt 
it is the winds which have now dried the lands of Cape Natal and Trans- 
vaal; it is they that have been the great agents in the work of drying up 
Central Asia, they have drunk the vast extent of water that formerly 
stretched from, the Euxine to the Caspian Sea, and from the Lake of Aral 
to the Gulf of Obi, and left steppes of salt in the place of this ancient 
Mediterranean. § 

It is by means of the atmospnfre, too, that the exchange of particles 
between the earth and bodies wandering in space is accomplished. When 
an aerolite, shot like an enormous bullet through space, meets the exteri- 
or strata of gas that surround the earth, it is instantly set on fire, and 
bursts either entirely or on the surface ; and hurling with violence some 
fragments to the ground, it leaves behind it a long train of luminous mat- 
ter resembling a fiery track. Owing to the resistance op23osed by the 
atmosphere to the passage of the strange star, the globe is every year en- 

* Fitzroy, Adventure and Beagle, vol. ii. Appendix, p. 89. 
t See The Earth, the section entitled Rivers. 
X Humphrey's and Abbot, Report on the Mississippi River, p. 450. 
§ Maury, Physical Geography of the Sea. 



210 THE ATMOSPHERE AND METEOROLOGY. 

riched in this manner with material brought from*the sky. The strata of 
air, moreover, are the vehicle of all sounds ; they also convey the vibra- 
tions of light and heat. Deprived of this envelope, the globe would im- 
mediately be wrapped^ in complete darkness. But if the atmosphere al- 
lows the rays of luminous heat emitted by the sun to pass, it intercepts 
in return a great part of the dark rays, which escape from the earth into 
space. It is thus that the globe has been able to preserve its normal 
temperature, and has become the theatre of life.* 

The atmosphei'e, which, as the common vehicle of exchange, is ever in 
motion, is also the great agent by which nature receives the wonderful 
colors that beautify her. It is owing to the reflection of the blue rays 
that the sky and the distant heights of the horizon assume that beaiitiful 
azure hue, which varies with the altitude of each region, the abundance 
of watery vapor, and the contrast of the clouds. It is owing to the re- 
fraction undergone by the luminous rays in passing obliquely through the 
aerial strata, that the sun is announced every morning by the vague glim- 
mers of twilight, then by the splendors of dawn, and thus shows himself 
before the astronomical hour of his rising. It is also due to an analogous 
phenomenon that in the evening he seems to slacken his descent below 
the horizon, and even after he has disappeared coloi'S the west for a long 
time with the purple of sunset. Without the gaseous envelope of the 
earth -spe should never see those varied plays of light, those changing har- 
monies of color, those gradual transformations of delicate shades, which 
form the marvelous beauty of our mornings and evenings. The special 
works on meteorology describe at length all these brilliant phenomena of 
the air, the rainbows, halos, parhelions, and that splendid spectacle of the 
" after-glow " which colors the snows and ice of the Alps with a rosy tint 
more than twenty minutes after the sun has set. Nothing is so beautiful 
as this phenomenon, due to the contrast of the lower slopes which are al- 
ready in the shade, and the high peaks which the solar rays reflected 
above the horizon still illuminate. When the Aiguille-Verte is already 
veiled in shadow, as well as the neighboring summits of Mont Blanc, the 
latter is truly transfigured by the light glittering on its snows. "We 
might think we then saw a form foreign to the earth ;" then all at once 
the flame is extinguished, the colors soTorilliant vanish, " to give place to 
an aspect that we may truly call cadaverous, for nothing approaches more 
nearly to the contrast between life and death on the human face than 
this passing from the light of day to the shadow of night on the high 
mountains."! 

The mirage is another singular optical eflect, due to the deviation of 
the rays of light which traverse the atmosphere. When the surface of 
the eai-th is much heated by the sun, the lower strata of air expand, 
and often become lighter than the strata situated above. If the air is 
agitated by the wind, it then rises, oscillating like the smoke that rises 

* Tyndall, Heat. 

t Nakey de Saussure, Annales de Chimie et de Physique, 1839. 



THE MIR AC, E. 



211 



from a high furnace, and the outlines of all objects seen through this va- 
por seem to tremble ; if a calm reigns in the atmosphere, all the objects 
bathed by the denser strata are reflected, as in a sheet of water, in the 
more expanded air, and all their images appear double ; hence the name 




Fig. 97. — Mirages atVerdon, at the mouth of the Gironde. 

of espeio (mirror) which the inhabitants 5f South America give to the mi- 
rage. In the midst of the arid desert, at hundreds of miles from any 
stream, bushes and rocks are reflected in the air as in the basin of a fount- 
ain ; on the sea the ships, the shores, and signals are reproduced as on a 
second ocean ; even in the large squares of our cities which a burning sun 
strikes, the statues sometimes seem to bathe their feet in a crystalline 
water reflecting their graceful forms. This optical illusion, which thus 
paints imaginary objects even in our cities, is the " Fata Morgana " of It- 
aly, t.he deceptive " Delibab " of the Magyar puszta, and the " Thirst of 
the Gazelle " on the plains of Hindoostan. It shows from afar fresh oases 



F/ 












Fig. 9S.— Mirages of the Vincenncs and of the Peacock (after Wilkes). 



212 THE ATMOSPSEBU AND METEOROLOGY. 

♦ 

and ripjDling waters to the fatigued travelers, who, where the deceitful 
picture glitters, only find aridity, thirst, and jjerhaps death. In the des- 
erts of Arabia the plain seems every day transformed into an immense 
lake. In proportion as the sun sinks the magic sheet retires, then it fades 
completely away, to re-appear the next day an hour or two before noon.* 
The phenomenon of reflection is almost always accompanied by lateral 
movements which apparently alter the position of objects, in the same 
way as plates of glass of unequal thickness do ; we then see large masses 
of different forms detaching themselves to the right and left of the distant 
objects, and floating fantastically in the air. These phenomena of mirage 
are most curious in the polar sea^j^ already strewn with blocks and ice- 
bergs of every variety of contour. The surface of the ocean bristles with 
points, needles, crests, and overhanging cornices, which separate, rejoin 
each other, and then vanish, to re-appear again. Nowhere do we see more 
astonishing phantasmagoria. As to the prodigious scenes that the mi- 
rage is said to present to the eyes of the traveler,*by showing him forests 
of palm-trees, temples with colennades, caravans, armies on the march, 
and people gathered for fetes, they are probably in great part produced 
by fever under the ardent sun ; for in this fiery atmosphere, which floats 
above the whitened plains and reflects the splendor and the heat, the 
head is burning, the imagination excited, and the eye sees no longer any 
thing but the forms of fancy. 

* Palgrave, A One Yearns Travel in Central Arabia. 



* WEIGHT OF THE AIM. 213 



CHAPTER n, 

WEIGHT OF THE AIE. — HEIGHT OP THE UPPER STRATA. — BAROMETRIC 

MEASURES. 

The weight of the aerial particles, which makes itself felt in so terrible 
a manner in hurricanes, is relatively very small, since a litre of air (nine- 
tenths of a quart) taken at the surface of the ground, and at the tempera- 
ture of zero, weighs 770 times less than a litre of water. But the atmos- 
pheric mass surrounding the globe is such that, if it were to be entirely 
agglomerated in a single ball, it would weigh as much as a sphere of cop- 
per nearly sixty-three miles in diameter; that is, the twelve hundred 
thousandth part of the mass of the earth.* The pressure exercised by 
the atmosphere on a man of middle size is not less than fourteen or fifteen 
tons ; it is true, however, that this pressure, making itself felt at the same 
time in all directions on our frame, is by that very fact neutralized. 
We know that a column of air on any point whatever of the earth is 
equivalent, on an average, to that of a column of water of thirty-two feet, 
or to thirty inches of mercury ; it is the knowledge of this fact that has 
enabled us to construct the barometer. 

^till, if we know the weight of the atmosphere, we can not yet say in a 
jDositive manner to what distarfce it rises in space. If the higher aerial 
strata had the same density as those on the surface of the sea, the total 
thickness of the air would not exceed five miles, and, consequently, the 
highest mountains of the earth, the Gaourisankar, the Kinchinjunga, the 
Dapsang, and many others, would raise their peaks into empty space 
above the atmosphere. But it is not so ; above the lower strata, com- 
pressed by the weight of all the superincumbent aerial mass, the particles 
separate in proportion as the pressure diminishes, the air becomes rai'er 
and rarer in the heights of space, and ends by being completely lost, like 
the thin fluid which composes the tail of comets. According to the calcu- 
lations of Laplace, it is at more than 26,000 miles above the surface of 
the earth that, in consequence of the increase of centrifugal force, and the 
diminution of the weight, the aerial particles which may still be in space 
must forcibly escape from the terrestrial orbit. Perhaps it is, in fact, in 
these elevated regions at the very limits of the spheres of attraction of 
the heavenly bodies, that the exchange of their gaseous particles takes 
place. However that may be, it is at a height very inconsiderable in com- 
parison with the extreme limit indicated by Laplace, that the atmosphere 
ceases to be respirable by man. At the summit of Etna — that is to say, 
at an elevation of two miles — we have nearly a third of the aerial mass 
imder o-ur feet. At three miles and a half, a height above which a great 
*■ Sir Jolin Herschel, Meteorology, p. 16, 



214 TEE ATMOSPEEBE AND METEO^OLOaY. 

many mountains raise their peaks, the column of air which rests on the 
ground has already lost one-half of its weight ; consequently, all the gas- 
eous mass which extends far into the sky to immeasurable distances, is 
simply equal to the aerial strata compressed into this lower region. 

More than two hundred years ago, Periei', following the indications of 
his brother-in-law Pascal, established by the first direct experiment the 
diminution of the weight of the air in a vertical direction : he ascended 
Puy-de-D6me with the barometer in his hand, and during the ascent the 
column of inercury which measured the atmosj^heric pressure never ceased 
to sink gradually in the tube, and thus the means of measuring the height 
of mountains above the level of the sea, by simply reading the barometric- 
al indications, was discovered. Since this epoch science has made great 
progress, the precise law of the decrease of the wgight of the air and all 
other elastic gases has been brought to light by Mariotte, and innumer- 
able travelers have been able, with the aid of the barometer, to indicate 
approximately the altitude of the salient points in the vai'ious countries 
that they have traversed. Nevertheless, one can never be sure that the 
barometer has furnished perfectly exact measures of height. In each 
barometric reading we must take into account the temperature, the quan- 
tity of watery vapor contained in the atmosphere, the agitation of the 
winds — in a word, all those physical conditions of the air whose weight 
we are about to measure, and each of these secondary observations makes 
a greater or less correction necessary in the final result. The direct re- 
sults obtained by trigonometry are at present the only ones that give in 
an exact manner the height of the surface. 

To ascertain the altitude of summits another means is also employed, 
which, in consequence of the defectiveness of the instruments, generally 
gives results still less exact than those of the barometer. This means 
consists in measuring the heat of boiling water. In fact, the boiling- 
point, or the temperature at which the tension of the vapor of water ex- 
actly balances the atmospheric pressure, must necessarily sink in propor- 
tion as the pressure diminishes. It has been calculated that the aver- 
age fall of boiling-point is 18° Fahrenheit for every 1062 feet of vertical 
height. But experiments may give for the heights of mountains difier- 
ences of many hundred feet. Thus, Tyndall found, in August, 1859, that 
the temperature of boiling water on the summit of Mont Blanc was 84*97°, 
while in the preceding year he had observed a slightly lower boiling- 
point on Mont Rosa, though this latter peak is five hundred and fifty-eight 
feet lower than the giant of the Alps. * 

To what height is the air dense enough for a man to be able to find the 
oxygen necessary for his lungs, and to live there for a few seconds at 
least ? The climbers of mountains have never reached this extreme limit, 
because of the fatigues of the ascent, which add to their difficulty of find- 
ing a sufficient quantity of air. Thus the highest peaks of the Himala- 
yas and the Andes have remained to this day untrodden by human foot.* 
* See The Earth, the section entitled Mountains. 



AERONAUTICAL EXPEDITIONS. 215 

At the summit of Ibi-Gamin, the highest point yet scaled in an ascent,^ 
Robert Schlagintweit, found himself at an elevation of four miles and a^P 
quarter. The barometer was only 13 "3 inches, so that the traveler had 
beneath him nearly three-fifths of the mass of air. 

Nevertheless, thanks to the balloon, aeronauts have been able to as- 
cend to heights which even the condor does not reach, and from whence 
the highest mountains would appear as if they rose from the depth of an 
abyss. In 1804, Gay Lussac ascended to four miles and a half; in 1851, 
Barral and Bixio ascended a little higher; in 1858, Rush and Green rose 
to five miles. But these are all altitudes inferior to the highest summits 
of the continents. Finally, on September 5, 1862, Glaisher and Coxwell 
undertook an aeronautic expedition, in which they resolved to ascend as 
long as they could preserve the sense of their own existence. The air 
becoming too rare for their lungs, hardly allowed them to pant ; they had 
palpitations of the heart, singing in the ears, the blood swelled the arte- 
ries of their temples, their fingers froze and refused to move ; but their 
will sustained them, they threw more sand from the car, and thus gave 
themselves a new impetus into the atmosphere, Glaisher fainted away, 
but his companion did nothing to arrest the ascent ; his eyes fixed on the 
instruments, he noted with a glance the gradual sinking of the column 
of mercury in the barometer and thermometer, as if he were in the ob- 
servatory at Kew. Gradually taken possession of by torpor, the aeronaut 
lost the use of his hands ; but he still held the cord of the valve between 
his teeth ; and when he felt that but one single second separated him and 
his friend from death, then he let the gas escape, and the balloon was ar- 
rested, and descended gradually toward the plains, situated at six and a 
half miles, or perhaps at six and three-quarter miles below, for the col- 
umn of the barometer was only at 6*5 inches. What noble courage on 
the part of these men risking death with such simplicity of soul, and for 
the sole advantage of studying the temperature of an atmosphere where 
neither man nor bird can live ! Certainly, it would greatly lower the 
force of soul and philosophical calm to compare it to the brutal courage 
of the soldier rushing into the thickest of the furious melee, intoxicated 
with powder, din, and blood. 

At the height to which Glaisher and Coxwell rose, they had nearly 
four-fifths of the weight of the atmospheric strata beneath them ; the re- 
maining fifth, where the air is too rarified for the lungs of man, rises di- 
lated more and more to unknown heights. We can, however, ascertain 
the presence of the aerial fluid much above the space to which man has 
been able to ascend. In truth, the refraction of the solar rays in the 
dawn and twilight has permitted us long ago to calculate that the appre- 
ciable part of the atmosphere rises to at least forty-five miles, and, owing 
to the perfection of optical instruments, the visible limits of this ocean of 
air which bathes our globe have gradually retreated. In supporting the 
observations made in tropical regions on the phenomena of the twilight, 



216 TKE ATMOSPEEBE AND METEOROLOGY. 

M. Emmanuel Liais believed he could affirm that the height is in reality 
Hwo hundred and even two hundred and ten miles.* 

By this the real diameter of the earth would be increased by about a 
tenth. Though this atmospheric stratum is usually left out of the calcu- 
lations of astronomers on the dimensions of the planet, it ought neverthe- 
less to be measured as an integral part of the earth. 

* Les Espaces Celestes et la Nature Tropicale. 



MEAN PRESS TJRE OF TEE A TMO SPHERE. 2 1 \ 



CHAPTER III. 

MEAN PEESSUKE OF THE ATMOSPHERE UNDER VARIOUS LATIDUDES. — DEN- 
SITY OF THE AIR IN THE NORTHERN HEMISPHERE. DIURNAL OSCILLA- 
TIONS OF THE BAROMETRICAL COLUMN. — ANNUAL OSCILLATIONS. — IRREG- 
ULAR VARIATIONS. — ISOBAROMETRIC LINES. 

Tnif atmosphere is of such mobility that its weight, measured in an ex- 
act manner by the column of mercury in the barometer, varies incessantly 
all over the earth. The various meteoric changes, from cold to heat, from 
dryness to moisture, augment or diminish the pressure of the air, and in 
consequence a corresponding oscillation is produced in the mercury con- 
tained within the tube of the instrument. Now, any volume of mercury 
being about 10,500 times heavier than the same volume of air taken at 
the level of the ocean, we must conclude from this that every movement 
of the barometric column reveals a change 10,500 times greater in aerial 
space. 

When air is heated either by the direct influence of the sun or by a cur- 
rent of higher temjjerature, its particles expand, become relatively lighter, 
ascend into space, and then spread out laterally. The pressure then di- 
minishes, and in consequence the column of mercury in the barometer 
must fall. The contrary takes place when the air is condensed by cold, 
and .when the aerial masses flow together to fill up the space ; the weight 
of the atmosphere is increased, and the level of the mercury rises In the 
instrument. This is the reason why the fall of the barometer indicates 
generally an increase of temperature, while a diminution of heat is marked 
by the contrary phenomenon. The barometer and thermometer oscillate 
in inverse ways. It is true that the air can absorb so much the more wa- 
tery vapor the warmer it is, and in this Avay the pressure which is dimin- 
ished on one side by the ascent, and the lateral flow of the aerial fluid, is 
augmented on the other by the increase of vapor contained in the atmos- 
phere ; air becoming colder, on the other hand, loses its capacity of dis- 
solving the wateiy vapor, and grows lighter in proportion. Thus the 
phenomena counterbalance each other, and it is not without numerous ob- 
servations treated with sagacity that we are able to distinguish that 
which, in slight barometric oscillations, ought to be attributed either to 
the pressure of the pure air, or to that of the watery vapor. As to the 
abrupt variations, in respect to which we can not be mistaken, they are 
sometimes enormous ; there are even some which are marked in the col- 
umn of mercury by a diflerence of two or three inches, one-fifteenth of 
the total height. A tempest in the ocean of the air is the cause of this 
agitation of the liquid in the instrument.* 

* See below, the section entitled Hurricanes. 



218 



THE ATMOSPHERE AND METEOROLOGY. 



The pressure of the atmosphere varies over all the earth, and we can 
not yet indicate it with exactitude for the entire globe. It is probable, 
however, that at the surface of the sea it exceeds on an average, by a 
slight fraction, the amount of 29 '90 inches. Toward the equator the ordi- 
nary pressure is only 29'84 inches; but from the tenth degree of latitude 
in the two hemisjDheres the pressure increases little by little, and toward 
the thirtieth or thirty-fifth degree it attains its maximum, 30 or 30 "OS 
inches. From thence, in the direction of the poles, the pressure dimin- 
ishes; toward the fiftieth degree it is 29*92 inches, and farther north 
29"76 inches only. Thus it is at about an equal distance between the 
pole and the equator that the air exercises, on an average, its greatest 
pressure on the barometric column ; nevertheless, there being much more 
watery vapor in the aei'ial strata of the temperate zone than in those of 
the polar zone, it is probable that, the air being perfectly dry, its pressure 
would continually increase from the equator to the poles more or less reg- 
ularly in proportion to the sinking of the temperature. This is, moreover, 
a phenomenon rendered very probable by the rise in the barometer, which 
is ordinarily produced by the transition from heat to cold. However it 
may be, the researches of Sir James Ross and Wilkes in the southern seas 
establish the fact that, on an average, the barometer is slightly higher in 
the northern than in the southern hemisphere. We must necessarily con- 
clude from this that a greater quantity of air is accumulated over that 
half of the earth where the continents are grouped. Thus, as Sir John 
Herschel i-emarks, the current of a river is always rippled above an un- 
equal and stony bed ; and in the same way the atmosphere must swell in 
waves above the continental masses. This best explains the astonishing 
conti'S.st between the two hemispheres.* 



29322 "f^ 



2a225"^J 



29.528*^' 




Abo 



Cnmana 



Noon 



9^ Mdmlhi 15^ 



Ocean Eqtialatoiid 



Noon 



Pig. 99.— Tropical hours of tiie Equatorial Ocean, of Cumana, of Halle, aud Abo. 

If the normal pressure of the atmospheric strata varies at the level of 
the ocean under difierent latitudes, it varies also all over the eai»th, ac- 
cording to the hours and seasons ; it obeys the rhythm of time as well as 
that of space. Every day the aerial mass oscillates twice in inverse di- 
rections. In the morning, toward four o'clock, the barometric column pre- 
sents a first minimum of height, but it rises gradually, and toward ten 
o'clock in the morning it attains its highest elevation ; afterward the press- 
ure of the air diminishes till toward four o'clock in the evening, the time 
* W. Ferrel, Motions of Fluids and Solids, p. 39. 



BITJRNAL OSCILLATIONS OF BAROMETER. 



219 



when the barometer is at its minimum of height. The column of mercury 
then begins to rise till ten o'clock at night, to sink again for six hours ; 
tlie periods of the day during which these changes occur are known un- 
der the name of " tropical hours." The curve of variations, as we see by 
the cut on the opposite page, is much more regular in the equatorial than 
in the temperate zone. 

What is the cause of this double daily oscillation ? Many meteorolo- 
gists formerly recognized in these movements of the barometer regular 
tides, similar to those in the ocean, and, like them, obeying the combined 
influences of the sun and moon. Bat these oscillations always occur, on 
an average, at the same hours, and do not present at the epoch of syzy- 
gies and. quadratures phenomena corresj^onding to those of the ebb and 
flow.* The researches of Aime, of Flangergues, and other natural philos- 
ophers have, it is true, established the existence of an aerial tide ; but the 
amplitude of this movement is very slight in comparison with that which 
occurs between the tropical hours. It is, therefore, by the combined in- 



03.5221115)— 



45.628 ins 



Q^. 2l3 105 




Spring 
Winter 



Arcrage for 
the 'year 

Summer 
Aiit iimn 



Soon 



6^ 9^ MSdn^t \9^ 18^ 

Fig. 100.— Pressure of dry Air at Apenrade. 



21^ Noon 



fluence of the heat of tli^ day and the pressure of watery vapor that we 
must explain, with Dove, the two movements of rising and falling, which 
take place every day in the column of mercury. Commencing in the cold 
hours of the morning, the gradual increase of temperature must result in 
expanding the atmosphere, and making the barometer sink. But while 
the pressure of the air diminishes, the quantity of watery vapor augments 
rapidly, and its pressure, added to that of the air, produces a sort of tem- 
porary , wave, aftoi' which the barometric column continues to fall, to rise 
again with the nocturnal cold. If the pressure of the watery vapor dis- 
appeared from the atmosphere the barometer Avould rise regularly in all 
seasons toward the middle of the night, and would be at its lowest to- 
ward the middle of the day. This is shown by the above figure, repre- 
senting the barometric oscillation of the dry air at the port of Apenrade, 
* See, above, the section entitled The Tides. 



220 THE ATMOSPHERE AND METEOROLOGY. 

on an estuary of the Baltic. In very dry countries, such as Eastern Sibe- 
ria, the pressure of the watery vapor is too slight to counterbalance the 
action of temperature, and in consequence only two oscillations occur dur- 
ing the four-and-twenty hours, a fall with the increase of temperature, and 
a rise with the cold of night. 

The diurnal movements of the barometer are much more regular and 
more easily ascertained in the equatorial regions and near the level of the 
sea than under high latitudes and in the interior of continents. This is be- 
cause over the tropical seas the alternations of temperature, evaporation, 
and precipitation succeed each other, like all other physical phenomena, 
with greater regularity than in other parts of the globe. Besides, it was 
in the equatorial seas that the diurnal oscillation was observed for the 
first time, and it was in these same latitudes that Humboldt was able to 
ascertain the hours exactly. In the temperate regions these regular move- 
ments of the barometric column are in a great measure hidden by the 
abrupt leaps of the mercury, obeying the constant variations of the atmos- 
phere ; it is, therefore, only after a longer or shorter series of days, or even 
weeks, that meteorologists can, by establishing averages, reveal normal 
oscillations analogous to those which occur at the equator. In the high 
mountain regions it is still more difficult to ascertain the regular succes- 
sion of the barometric waves, for the changes which occur in the lower 
strata of the air are only felt later, and are variously mixed in the higher 
strata. Thus the rising of the barometer which takes place toward ten in 
the morning at Zurich, does not occur on the summit of the Righi till two 
o'clock in the afternoon, and only at three o'clock on the Faulhorn ; often 
the depi'ession of the barometric column does not even make itself felt in 
the afternoon on these heights, and each day presents but a single great 
oscillation. 

The annual variations of the pressure of the air present alternations 
analogous to those of the diurnal variations. In th§ tropical countries, 
where the seasons follow one another with great regularity, and in the 
interior of continents, the air of which contains .but a slight quantity of 
watery vapor, the mercury of the barometer gradually sinks from winter 
to summer in inverse proportion to the heat, and re-ascends with the cold 
from summer to winter. At Calcutta, at Benares, in Hindoostan, as at St. 
Petersburg, in Prussia, and at Nertschinsk, in Siberia, the maiximum of the 
pressure of the air is perceptible in the month of January, while the mini- 
mum occurs in the month of July. The atmosphere is now heavier, now 
lighter in each hemisphere, according to the regular alternations ^f heat 
and cold.* Thus, as the following figure shows, the annual variation in the 
pressure of the air occurs in the same manner in all the countries situated 
on the same side of the equator ; but the phenomenon is much more strik- 
ing in tropical climates than under high latitudes. In the greater part of 
the countries of the temperate zone, and, above all, on the shores of the . 
ocean, the pressure of the watery vapor during the summer increases con- 



ANNUAL BAB03IETRia VARIATIONS. 



221 



siderably, and thus, counterbalancing tbe normal effect of dry air, gives to 
the barometric curve a maximum of summer Avhich corresponds to the di- 
urnal rise of ten o'clock in the morning, or else complicates the series of 
monthly variations by very numerous irregularities. Each one of these 
inflections corresponds to some important phenomenon in local climate, 
cold or heat, storms or tranquillity of the air, dryness, or a great quanti- 
ty of watery vapor. In general, it is at the epoch of the equinoxes, when 
the temperature is nearly equal to the annual mean, that the mean baro- 
metric pressure of the year is established. 

HCniinCtPflS 

170 

30.515iiis) 



(50 .119 ins) 



760 
(29.922 ms) 



, i55 

(29725 ins) 



750 

(29.3i8ins> 



2^5 

(29.551 ins) 



{29J34ins)D 



Fig. 101 — Monthly Variations in the Pressure of the Atmosphere at Cairo, Calcutta, Berlin, 
St. Petersburg, "Benares, Paris, and Halle. 

As to the irregular variations, they are also accomplished according to 
a certain rhythm in various regions of the globe. At the equator they 
are almost nothing, but in proportion as we approach either of the poles 
the irregularities become more marked, and the leaps produced in the col- 
umn of mercury by sudden changes of temperature, and by the alterna- 
tions of winds and storms, succeed each other more frequently. In trop- 
ical regions these diflierences of barometric height are hardly a few frac- 
tions of an inch, while in the temperate latitudes they have exceeded 2-1 
inches at Milan for a period of eighty-one years, and 2*6 inches at St. Pe- 
tersburg for a period of nineteen years. In order to obtain figures more 
comparable with each other, Kamtz has calculated the monthly amount 
of the oscillations of the barometer for every station, and in this way has 
been able to draw »p the following table: 




222 



THE ATMOSPHERE AND METEOROLOGY. 



Latitude. Monthly Barometric Amplitude. 

0°tolO° '. 0-1 inches. 

10° to 20° , 0-17 

20° to 30° 0-32 

30° to 40° 0-53 

40° to 50° 0-81 

50° to 60° 1-03 

60° to 70° 1-2 

Still, we must not expect to find exactly the same amplitude per month 
at all the points situated at the same distance from the equator. In this 
respect, on the contrary, we observe great diversities, which we must at- 
tribute to the diiFerence of continental forms and of climates. By uniting 
with each other all the points in which the same monthly variation in the 
pressure of the air occurs, we obtain a series of lines called isoharometric, 




10° 20° 30" iOo 50° 60° 20'' 

Fig. 102.— Monthly Amount of the Oscillations of the Barometer in the Northern Hemisphere. 

which all curve to the north across the Atlantic, and, on the whole, much 
resemble the lines called isothermal.^ These are curves imagined by 
Kamtz, which indicate the true latitude for the general movements of 
the atmosphere. In spite of the extreme mobility of air, in spite of the 
tempests which roll with fury from one point to another of the horizon, 
and disturb for a moment the regularity of atmospherical •phenomena, 
these lines maintain from year to year their mean direction ; while indi- 
cating the disturbances of the air, they show, by their permanence and 
their regularity, how much these commotions depend on the great laws 
which rule our planet. 

* See below, the section entitled Climates. 



CIRCULATION OF THE WINDS. 223 



CHAPTER IV. ^. 

GENERAL LAW OF THE CIRCULATION OP WpjDS;^^— TRADE-WINDS FROM THE 

NORTH-EAST AND SOUTH-EAST. EQU^ATORTAL CALMS. OSCILLATION OF 

THE SYSTEM OP WINDS. 

In the continental regions, and principally in those of the temperate 
zone, it would often be difficult to recognize at first the general law 
which presides over the movements of the atmosphere, for these various 
oscillations may be modified by a crowd of local circumstances, such as 
the direction and height of mountain chains, the extent of plains, the con- 
tours of the shores, the abundance or scarcity of vegetation. Even in one 
day tli£ winds will sometimes blow successively from all points of space, 
and among these rapid changes to which the atmospheric currents are 
subject it is not always possible to ascertain with certainty the normal 
direction of t-he mass of air in movement. To understand the laws of the 
atmosphere in their simplicity we must transport ourselves to the equa- 
torial regions of the ocean, above which the sun describes each day its im- 
mense semicircle in the space of twelve hours, and where all the move- 
ments of nature, regulated by the uniform march of the sun, have some- 
thing of the rhythm of the celestial cycles. It is there that we may seek 
the first displacement of the atmosphere, which travels as an immense 
sheet of air all round the globe. We are there pi-esent at the birth of the 
winds. It is thei'e that ^olus would be seated if the gods still lived. 

During the days of summer we perceive from afar a vibratory motion 
of the air over the heated earth, a kind of vaporous trembling, doubtless 
rendered visible by the incessantly changing mirage of objects lying be- 
yond.* This is because the strata of the atmosphere reposing on the 
ground have gradually expanded, and rise in spirals through the colder 
and denser medium which Aveighs upon them. In the same way the rare- 
fied air of furnaces mounts rapidly toward the upper regions whither its 
relative lightness carries it. 

A similar movement is produced on a very large scale in the equatorial 
regions. The great force of the sun's rays making themselves princijDal- 
ly felt in these countries of the world, the aerial strata expand under the 
influence of the heat much more than in other latitudes. They become 
lighter, and rise rapidly into space, as is shown by the slight pressure of 
the air on the barometric column. f Thus a void is formed, which the ad- 
jacent masses of air hasten to fill, and two horizontal currents go to feed 
the great vertical current which ascends toward the higher strata of air 
in the equatorial regions. But these horizontal currents themselves leave 
spaces behind them toward which new masses of air rush ; the atmos- 
* See above, p. 212, t See above, p. 213. 



224 THE A T2I0 SPHERE AND METEOR OLOGY. 

pheric waves move nearei- and nearer through all the zones as far as the 
polar, ice, and from the two ends of the planet they march toward the 
equator, where the ascendmg movement of the overheated air summons 
them. Two winds, the one from the north, the other from the south, take 
their origin from the midst of the ice of the two opposite poles to meet at 
the equatorial circle. 

If the earth were not carried by a movement of rotation ai-ound its 
axis, the atmospheric currents would flow directly toward the equator, 
without deviating to the right or left from the lines of the meridian. The 
northern current would flow in a straight line to the south, the southern 
current would direct itself exactly toward the north, and they would meet 
in direct opposition in the equatorial regions. But it does not happen 
thus, because of the rotation of the globe from west to east. The speed 
of this movement varies for each point of the tei'restrial surface, as the 
diameter of its latitude ; while it is nothing at the poles, it is five hun- 
dred and twenty miles per hour at the sixtieth degree of latitude north 
or south; at the equator itself it is 1050 miles. The mass of air which 
flows from the poles toward the tropical zone thus travels successively 
over latitudes whose own speed around the axis of the globe is greater 
than theirs ; consequently they are compelled to deviate farther and far- 
ther toward the west in the opposite direction from the general move- 
ment of the earth. Instead of being directed perpei;idicularly toward the 
equator, to form with it an angle of ninety degrees, the aerial curi-ents 
coming from the poles strike the equinoctial line obliquely at an acute 
angle. Thus the same planetary phenomenon that causes the deviation 
of the flow of water* of the oceanic currents,! and perhaps even, accord- 
ing to M. Musset, the swelling of the trunks of trees in the direction from 
east to west, sufiices likewise to put in motion the whole mass of the at- 
mosphere. The rivers of the air reproduce, only in greater proportions, 
on account of their larger domain, the immense curves of the oceanic cur- 
rents. The two fluids in movement, winds and marine currents, are su- 
perposed in their march around the planet. 

In the tropical zone, where the incessant attraction produced by the as- 
cending current determines a constant afilux of masses of air coming from 
the north and south, the circulatory system of the winds possesses in gen- 
eral a tolerable regularity. In this part of the terrestrial sphere the ae- 
rial masses move uniformly, tht)Sfe of the northern hemisphere in the di- 
rection from north-east to south-west, and those of the southern hemi- 
sphere in the dii-ection from south-east to north-west. Thus two atmos- 
pheric currents do not cease to flow obliquely to meet each other. These 
are the " trade-winds," which the ancients hardly knew, and of which the 
complete discovery was reserved for the great Spanish and Portuguese 
navigators. Among all the marvels that they discovered in the tropical 
regions, none astonished them more than these breezes, blowing invaria- 
bly from the same point of the horizon. Accustomed to the changing 
* See The Earth, the section entitled Rivers. t See above, p. 94. 



THE TRADE-WINDS. 225 

and irregular winds of the European seas, the sailors were almost terrified 
at the constancy of these winds, which carried them toward the equator, 
and never flowed back again in the direction of their country. The com- 
panions of Columbus saw in it the efiect of the craft of the devil, and ask- 
ed with terror if all this movement of the aerial waves was not directed 
toward some gulf situated at the limits of the world. Nevertheless, nav- 
igators were soon familiarized with the tranquil latitudes traversed by 
the trade-winds. The Spanish sailors formerly called the tropical part 
of the Atlantic Ocean el golfo de las Damas (the ladies' sea), because 
there one could confide the helm of a ship to a young girl without dan- 
ger. Indeed, according to Varenius, the sailors setting out from Acapul- 
co could fall asleep without pajjitog attention to the rudder, with the cer- 
tainty of being conducted by the wind across the calm waters of the Pa- 
cific to the shores of the Philippines. Struck with the great advantages 
which the constancy of the trade-winds present to navigation, the English 
have given them this name. The old term, vents alizes, by which the 
French sailors designate them, indicates an equal, continuous, and regular 
movement. 

Still, it must be said, these winds have not such a certain njarch that 
we can count on them as on the return of the heavenly bodies. The al- 
ternation of the seasons and the great atmospheric disturbances make 
them oscillate from right to left, retard or accelerate them, and sometimes 
even neutralize them for a time. In the neighborhood of the coast, the 
extremes of heat and cold which succeed each other on the continents 
cause the winds to deviate in their course,* and consequently it is only in 
the open sea, at a great distance from the coast, that the sails of ships 
are swollen by a breeze blowing almost constantly from the same point 
of the horizon ; but even then the wind is sti'onger in the morning and 
evening than during the heat of the day. In the Atlantic, bordered on 
each side by continents tolerably regular in form, the trade-winds have 
the most uniform speed. In the Pacific, the multitude of islands scatter- 
ed over the surface of the waters modify greatly the normal condition of 
the winds, and over a very great extent of their natural domain the trade- 
winds are transformed into monsoons. To the north of the equator the 
north-east winds only blow in a constant manner, between the Revillagi- 
^do and the Marianne Islands. As to the southern trade-winds, they are 
still more restricted ; they commence w4th the group of the Gallapagos 
at 1620 miles from the coast of America, and toward the west, they do 
not pass the Archipelago of Noukahiva and the Low Islands.. 

In rushing one against the other, the two opposite winds hold each oth- 
er in check, and consequently their force is neutralized ; it is thus that a 
circular zone of calms, variable winds, and sudden aerial eddies is formed 
all round the earth, which, according to the seasons, occupy a breadth of 
from one hundred and fifty-five to six hundred and twenty miles on the 
surface of the sea. Nevertheless, we must not suppose that, in this zone 

* See below, Fig. 107. 
15 



2«26 THE ATMOSPHERE AND METEOROLOGY. 

of so-called calms, the air is generally tranquil ; but the atmosphere is 
more often in a state of equilibrium there than in any other part of the 
surface of the globe. According to the Pilot Charts of Maury, the mean 
duration of the calms of the Atlantic between the fifth and eighteenth 
degrees of north latitude is to that of the winds in the proportion of nine- 
ty-eight to eight hundred and two, or of one to eight. During the period 
when the calms are most frequently produced — that is to say, in the month 
of ISTovember — and in the space comprised between the twelfth and thir- 
teenth degrees of north latitude, they prevail on an average half as much 
as winds coming from any point whatever of the horizon. 

We can understand that this zone, which separates the two trade-winds 
of the north and south, must necessariljf|be altered according to the sea- 
sons by the position of the sun, since it occupies on the circumference of 
the globe precisely those latitudes where the atmospheric strata are most 
strongly heated by the solar rays, and where the vertical movement 'of 
the expanded air is produced. When the sun, after the 21st of Septem- 
ber, crosses the equatorial line to tend toward the Tropic of Cancer, the 
centre of the trade-winds, and consequently of the band of calms, moves 
at the same time toward the north; on the contrary, when the sun re- 
turns to the Tropic of Capricorn, the most heated zone of air is gradual- 
ly brought back to the south with the whole circulatory system of the 
trade-winds. At the end of March the northern limit of the equatorial 
calms of the Atlantic is found, on an average, toward the second degree 
of north latitude, while at the end of September this same limit attains 
ordinarily the thirteenth or fourteenth degree.* As to the southern limit, 
it oscillates in the same ocean from one to four degrees of north latitude.f 
In the equatorial regions of the Pacific, the zone of calms is similarly dis- 
placed from month to month, following the march of the sun, and its 
breadth varies from one hundred and thirty-five miles in the month of 
February to more than eight hundred and forty miles in the month of 
August. J In this respect the analogy is almost complete in the two great 
oceans. In consequence of this annual periodicity, the whole aerial system 
incessantly oscillates according to the relative position of the sun ; and it 
is for this reason that, in the northern hemisphere, the north winds, being 
violently attracted toward the south, are much stronger in winter. Be- 
sides these, there probably exist monthly and semi-monthly oscillations 
resulting from the declination of the nioon.§ 

The central part of the zone of calms, which may be considered as the 
meteorological equator of the world, does not correspond with the equa- 
tor properly so called. On the earth, as in the higher organisms, the prin- 
cipal seat of life is placed out of the geometrical centre. The complete 
system of the winds inclines toward the northern hemisphere, and it is 
to the north of the line that the girdle of the equatorial calms is at all 

* D'Apres; — Dove, La Lot des Tempetes (traduction Legras), p. 17. 

t Horsburgh, East India Directory, vol. i., 25. 

t KerhaUet, Considerations Generates sur l' Ocean Pacijique. § Keller, Rennell. 



OSCILLATIONS OF THE WINDS. 227 

seasons developed. This phenomenon, which might seem at first sight 
strange, results from the grouping of the greater part of the continental 
lands in the northern hemisphere, and from the difference of temperature, 
which must be, at least for one part of the world, the result of this un- 
equal distribution of solid and liquid. It is also in the northern hemi- 
sphere that we find the Desert of Sahara, the true geographical south of 
the earth, that immense extent where wooded tracts are relatively few, 
and where the reflection from the burning sands and rocks vaporize the 
clouds which the atmospheric currents bring. The Sahara, and in a less 
degree all the tropical countries of the northern hemisphere, act as a great 
centre, toward which the aerial masses flow. It results, from the tables 
drawn up by Dove, that the mean temperature of the year is more ele- 
vated (92° Fahr.) toward the tenth degree north latitude than it is at the 
equator itself (91*5^ Fahr,), while the mean balance is stronger toward the 
twentieth degrefe of latitude (94° Fahr,) than in any other region of the 
world,* The high temperature of the continents thus forces the southern 
system of winds to encroach upon the northern system, 

* Dove, Vorbereitung der Wdnne auf der Oberjldche der Erde. 



•• 



228 THE ATMOSPHERE AND METEOItOLOOY. 



CHAPTER V. 

COUNTER TRADE-WINDS OR RETURNING WINDS. 

The aerial masses brought by the two trade-winds can not be inces- 
santly accumulated in the region of equatorial calms : they expand, rise 
to several miles of height, then, after having been mixed, and even par- 
tially crossed, they divide anew into two great returning currents which 
flow in an opposite direction in the upper regions of the atmosphere. 
Thus, as ^he natural philosopher Halley, who was the first to give a the- 
ory of the trade-winds, afiirmed nearly two centuries ago, it would be ab- 
solutely impossible, if these two atmospheric counter-currents did not ex- 
ist, that the equilibrium of the air could be established on the surface of 
the globe ; that which the breath of the trade-winds brings to the equator 
must necessarily be carrfed back by other winds toward the poles. The 
movement of the graceful clouds, so light that we see them from below 
floating in the heights of the air in the opposite direction to the trade- 
winds, is an incontestable proof of the existence of these higher returning 
currents.* Besides, two great volcanic explosions, often mentioned by 
savants, have also furnished striking testimonies which confirm Halley's 
theory in an indubitable manner. On the first of May, 1812, when the 
north-east trade- wind was in all its force, enormous quantities of ashes ob- 
scured the atmosphere above the island of Barbados, and covered the 
ground with a thick layer. From whence came these clouds of dust ? 
One would have supposed that they came from the volcanoes of the 
Azores, which were to the north-east ; nevertheless, they were cast up by 
the crater of Morne Garou, situated in the island of St. Vincent, at one 
hundred and twenty-five miles to the west. It is, therefore, certain that 
the debris had been hurled by the force of the eruption above the mov- 
ing sheet of the trade-winds into an aerial river, proceeding in the con- 
trary direction. In the same way, at the time of the terrible eruption 
of the volcano of Coseguina, in Central America, ashes were carried by the 
returning trade- winds to the shores of Jamaica, which is Ho less than eight 
hundred miles to the north-east of the crater whence they were thrown. 

On the coasts of Africa, and along the Mediterranean, grains of dust, 
almost imperceptible singly, give another vei^ remarkable proof of the 
existencw-of a great returning current in the high regions of the atmos- 
phere. Sometimes a shower of yellow or red dust, resembling powdered 
brick, falls from the sky. Ships which were in the neighborhood of Cape 
Verd, on the coasts of Morocco, or in the waters of the Mediterranean, 
have had their deck and sails completely sprinkled with these fine parti- 
cles. Humboldt, who had the opportunity to observe this rain, believed 
* See The Earth, the section entitled Volcanoes. 



The Ocean, A < 



SHOWERS OF 



~Gx"-efflila3acl: 



H-- 









A 



^<;wfoTinxlLarui 



T L 



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7 1-9 



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llie Azores 



Icel 



c 



c 



E A 



K 



1822 

18 Lf 



Cape cleY(;rdes 



l83o ;i521 



-Jf 7=:? - t Sv-Ay'""* 



'L: 



Eiv]^. iy Erhard 



HARPER &. B 



CANIC ASHES. 



PI,. XII 




j^iB'*. 



Uinol? 



i«.'>i; 



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1755<' 



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1 ^ -.o^. L ^'.'k- 



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ATranged bv A.Viiilleinin, aiter H.F.liiinb' i si 



iP.is, NKW YORK 



ALTITUDE OF RETURN CURRENT. 



229 



that it was composed of silicious dust raised by eddies of wind on the 
coasts of the Sahara, while the sailors who witnessed this phenomenon 
saw in it only a shower of sulphur. But Ehrenberg, with the aid of his 
microscope, revealed the nature of this dust, which is nothing else, at least 
in the Atlantic and the Mediterranean, than the silicious skeletons of an- 
imalculae coming from the llanos of South America. It is thus certain 
that these myriads of organisms, raised to a height in the air by the as 
cending current of the equator, have met above the trade-winds with a 
returning current, which has caused them to cross the immense basin of 
the Atlantic, and to reach the coasts of Africa, or even of Europe, as far 
as the basin of the Rhone, The aerial currents have thus become visible 
by means of these clouds of infusoria.* 







Fig. 103.— Cloud of Cinders from Morue Garou. 

In the equatorial zone the counter-current of the trade-winds can only 
commence at a height of from four to five miles above the level of the sea, 
for the highest summits of the Cordilleras remain entirely bathed in the 
lower current. The most southern mountain of the Atlantic basin, whence 
the returning wind has been observed, is the peak of Teyde, in the island 
of Teneriffe. There the masses of air flowing back from the equatorial 
zone are already sufliciently low to surround the terminal point of the 
volcano (only 12,060 feet high) at all seasons. In winter, when the whole 
circulatory system of the atmosphere has descended toward the south, fol- 
lo\ying the course of the sun, the returning current descends from the 
higher strata of the air, and strikes the surface of the water near the 
coasts of Portugal, then turns back again, and makes itself successively 
felt at Madeira, and on the middle and lower slopes of the peak of Ten- 
eriffe.f According to the astronomer Piazzi Smyth, it is at an average 
of 9000 feet of vertical height that the plane of separation between the 

* Maury, Physical Geography of the Sea. 

t Humboldt ; Leopold von Buch, Description des Canaries. 



230 



THE ATMOSPHERE AND. METEOROLOGY. 



two aerial rivers flowing in opposite directions is found. At the summit 
of the mountain the air is carried rapidly from south-west to north-east, 
while on the low parts of the island the trade-wind always blows with its 
habitual regularity.* The zone of clouds that it unrolls in an immense 
veil above the sea and the shores does not extend into that part of the 
heavens comprised between the two winds blowing different ways, but, 
on the contrary, it is found at a tolerable depth in the trade-winds. Be- 
tween the upper and lower currents the air is calm and free from clouds. 




104.— Island of Teneriffe. 



During the summer season, travelers who climb the sides of the peak of 
Teneriffe may confidently expect to find an unchanging sky directly after 
having passed the zone of clouds, from 900 to 1200 feet in thickness, which 
is spread like a second sea above the ocean.f At the change of the sea- 
sons, when the two oj)posing winds strive for victory on the slopes of the 
mountain, a few days are sometimes sufficient to bring about a change of 
3000 feet in the height of the intermediary zone. A battle between the 
two currents takes place in the sky ; soon the trade- wind mounts to the 
upper slopes of the peak ; now it is vanquished, chased from the heights 

* Philosophical Transactions, 1859. 

t See below, the section entitled Clouds and Rains. 



DIRECTION OF HOT AND COLD WINDS. 



231 



of the atmosphere, and driven with all its system of clouds toward the 
lower regions. It is principally above the pass of Laguna, between Santa 
Cruz and Orotava, that the combat takes place, and in consequence this 
district of the island is frequently inundated with rains. Piazzi Smyth 
has recounted these grand aerial contests at great length in his work on 
Teneriffe.* • 

In the Pacific Ocean analogous phenomena to those which occur in the 
Atlantic have been observed. Goodrich has ascertained that the normal 
current of the trade and returning winds make themselves felt at the same 
time, the one on the shores of the Sandwich Islands and the lower slopes 
of all the mountains of the Archipelago, the other on the summit of the 
volcano of Mauna-Loa. 

The direction of the upper counter-current is, like that of the trade- 
winds, determined by the rotatory movement of the earth. At its re- 
turn from the equator, each particle of air in movement turns toward the 
east, instead of deviating to the west, as in its voyage from the polar to 
the torrid zone. Aft^r having sojourned in the equatorial regions it trav- 
erses successively countries whose speed around the axis of the earth is 
less than its own. In proportion as it retreats from the zone of calms, it 
thus finds itself in advance of all the subjacent points of the planet, and 
changes into a wind from the south-west. Below it glides the north-east 
trade-wind, generally in an opposite direction ; but in consequence of the 
friction of the aerial particles, a stratum of calm air is formed between the 
two atmospheric currents, where all the meteoric phenomena due to the 
contact of the two masses, unlike in heat, moisture, and electric tension, 
are manifested. According to Dove, the counter trade-wind would bend 



NE- 



N.E. 




Fig. 105. -Theory of Dove 



X\<^ 



S."W 

Theory of Muhry. 



more and more to the east, because of the increasing curve of the earth in 
the direction of the pole. According to Miihry, on the contrary, the direc- 
tion of this wind would be exactly parallel to that of the lower current, 
and would curve gradually toward the north, in consequence of the at- 
traction exercised in the polar regions by the wind which descends to- 
ward the equator. This last theory appears the most probable ; but it is 
for direct observation to decide in a definite manner.f 

One might believe at first that the upper counter-current flows toward 

* Teneriffe, pp. 178, 174, 432, etc. 

t Mittheilungen von Petennannfix., 1866. 



232 



THE ATMOSPHERE AND METEOROLOGY. 



the pole, maintaining itself in the high regions of the atmosphere, and 
that the polar wind, on its side, more compact in its particles, because of 
the cold, always glides over the surface of the globe. It is only rarely 
that it is so. In a somewhat undecided region which, for the North At- 
lantic, oscillates alternately, according to the seasons, from the twenty- 
first to the twenty*fifth degree of latitude, the returning wind com- 
mences to descend from the heights of the sky to the surface of the sea, 
and strikes against the aerial masses which flow from the poles toward 
the burning latitudes of the equator. The zone where this shock of the 
winds occurs is considered as the outer limit of the trade-winds ; but it is 
incorrect to give it the name of the zone of tropical calms, for if the com- 
plete equilibrium of the atmosphere is more frequent there than in the re- 
gions bordering on the north and south, yet, nevertheless, the calms hard- 
ly last more than a day in the space of two or three weeks.* During the 
summer of the northern hemisphere, when the sun is at the zenith of the 
Tropic of Cancer, the counter trade-winds may make themselves felt with 
tolerable regularity, as far as the latitude of the no^h of Germany, or of 
St. Petersburg. In autumn and in winter the domain of these returning 
currents is unceasingly restricted toward the north, and increases to the 
south. Brest and then Lisbon are its extreme limits in the northern hem- 
isphere, till the sun resumes its march to the north. 




Fi?. 106. — Variations iu the Trade-winds. 



Why does the upper cun-ent thus descend from the heights of the at- 
mosphere during the greater part of the year ? Doubtless, because it car- 
ries with it enormous quantities of watery vapor, which renders it heavier 
than the cold dry air fi-om the poles. Owing to its temperature, it first 
* Lartigue, Maury, Pilot Charts. 



RELATIVE POSITION OF THE TWO WINDS. 233 

rises higher than the Cordilleras, then, being gradually cooled, it sinks 
under the weight of moisture that saturates it, and when it finally enters 
the temperate zone, it falls to the surface of the earth with clouds and 
rains, and strives for supremacy with the polar current. The difiference 
of specific cold between the opposed masses of air must be very small, 
since by turns each gains the advantage. Often the current coming from 
the torrid zone, recognizable from below by its trains of clrri^ can not 
reach the sui-face of the ground, and maintains itself as far as the pole in 
the upper strata of the atmosphere, while the wind that blows from the 
frigid zone forms a continuous current over the earth, from the pole to 
the equator. Still, we must consider the south-west wind as the prevail- 
ing wind of the northern tenfiDerate zone, for it makes itself felt there 
much more frequently than the contrary current, the proportion of the 
former being nearly double between the fiftieth and fifty-fifth degree of 
latitude.* We know that sailing vessels formerly required forty-six 
days, on an average, for the voyage from Europe to the United States, 
while the return, facilitated likewise by the Gulf Stream,f was accom- 
plished in twenty-three days. The winds from the south-west and west, 
which are nothing else than the counter-current of the trade-winds, blow 
with such regularity in these parts, that one might give the names of 
" ascending voyages " to the passages from Europe to America, and " de- 
scending voyages" to those in the opposite direction. Corresponding 
phenomena occur in the southern hemisphere ; there it is the north-west 
winds which blow most frequently beyond the southern limits of the 
trade-winds. 

Thus the two permanent winds which are drawn toward the equator 
by the expansion of the warm air have each their proper domain, limited 
in one direction by the calms of the equinoctial line, in the other by the 
irregular winds of the temperate zone. Still, these limits oscillate inces- 
santly from month to month and from season to season, and one can not 
indicate them in a precise manner. On a general map of the trade-winds, 
it is sufiicient, therefore, to trace the extreme frontiers of these currents 
for winter and summer.;); On an average, the space in the Atlantic over 
which the noVth-east wind blows embraces from eighteen to twenty de- 
grees of latitude, or from 1245 to 1275 miles; in the South Pacific the 
domain of the south-east trade-wind would not be less than thirty de- 
grees, § or 2045 miles. 

Between the atmospheric and oceanic currents the analogy is evident. 
The maritime river which is founded at the junction of masses of water 
coming from the two polar seas, corresponds to the equinoctial zone, where 
the trade-winds of the north-east and south-east meet. Obliged to ex- 
tend laterally while maintaining themselves under the common level of 
the maritime reservoir which contains them, the tepid waters of the equa- 
torial current flow afterward toward the north-east parallel to the coun- 

* Maury, Pilot Charts. t See above, p. 80. t See above, Fig. 106. 

§ Kerhallet, Considerations Generales S2ir V Ocean Pacijique. 



234 THE ATMOSPHERE AND METEOROLOGY. 

ter-current of the trade-winds which has risen into the heights of the at- 
mosphere. Under the influence of the same causes, the two oceans of air 
and water move in the same direction, and their movements are subject 
to the same oscillations to the north or south during each alternating pe- 
riod of the seasons. In summer, when the Gulf Stream is prolonged far 
into the northern sea, the double system of the north trade- winds and 
counter-winds advance several degrees into the temperate zone, while 
during the winter it flows back again toward the Tropic of Cancer, fol- 
lowed by the Gulf Stream, which bends gradually towai'd the south. 
The resemblance would be complete if the water were an elastic and com- 
pressible fluid like air, and were not inclosed in a basin whose borders it 
could not pass. The difference of the means explains the difierence of the 
currents which the heat of the sun and the terrestrial rotation produce in 
the ocean and in the atmosphere. 



LAND TRADE-WINDS. 235 



CHAPTER VI. 

THE TRADE-WINDS OF THE CONTINENTS. — THE MONSOONS. — ETESIAN WINDS. 

The trade-winds, as we said, have not the same regularity on the con- 
tinents as over the seas. On the surface of the ocean the masses of mov- 
ing air are not arrested by any obstacle ; they are propagated freely to- 
ward the equatorial zone, and can scarcely be turned from their route by 
the attraction of any marine centre of heat, as the temperature of the wa- 
ter only increases or diminishes very slowly, and the oscillations of the 
thermometer from day to night do not attain thirty-six degrees Fahren- 
heit. In the midst of the large islands and the continents it is no longer 
so. Their mountain chains oppose the course of the winds, and cause 
them to change their direction ; forests, prairies, sheets of inland waters, 
plateaux with long slopes, hilly countries, large plains, and the innumera- 
ble variations of topographical relief, are variously heated by the sun, and 
by this very circumstance turn aside or repel the wind which blows from 
the neighboring seas. In the higher regions the current can, it is true, 
continue its normal movement above the plateaux and the mountqj^s; 
but below the uneven surface of the country is traversed by irregular 
winds. Here the band of equatoi'ial calms is completely obliterated, there 
it is enlarged in an abnormal manner; the winds are deflected variously 
on one side or the other, and are directed toward that country whose air 
is most expanded by t\^ rays of the sun. Nevertheless, it must be said 
that only a very insufficient number of meteorological observations have 
as yet been made in the greater part of tropical countries. 

Still we can not doubt but that the trade-winds blow over vast conti- 
nental tracts, as well as over the surface of the seas. In fact, the want of 
rain and the almost complete absence of vegetation in all that part of Af- 

Irica known by the name of the Desert of Sahara, prove in an indubitable 
manner the existence of a regular wind from the north-east. After hav- 
ing passed the high plateau of Asia, and having discharged itself of the 
greater part of its wateiy vapor, this atmospheric current traverses ob- 
liquely the whole of Africa from the banks of the Nile to those of the Ni- 
ger. On this enormous tract of nearly 3000 miles it only lets rain fall on 
some mountain summits, such as the Djebel-Hoggar, and scarcely casts a 
single cloud on the unchanging azure of the sky. On tile western coast 
of the Sahara, the burning wind called the Sarmattan is nothing else than 
the north-east trade-wind more or less turned from its course because of 
the neighborhood of the sea. Toward the seventeenth degree of north 
latitude, on the southern frontiers of Soudan, clouds are at last formed in 
space, abundant rains penetrate the soil, and the aridity of the desert gives 
place to a fine vegetation; this is, because the domain of the permanent 



236 THE ATMOSPHERE AND METEOROLOGY. . 

winds terminates there, to be replaced by the zone of equatorial calms 
with an ascending current loaded with aqueous vapors. In the southern 
J)art of Africa, the trade-winds of the south-east make themselves regular- 
ly felt, and, according to the testimony of Livingstone, traverse the entire 
continent from the mouths of the Zambesi to the coast of Angola, On 
the other side of the great strait of the Atlantic, the tropical regions of 
South America are likewise refreshed by the constant breath of moist 
winds from the south-east. Brazil, Paraguay, a great part of the Argen- 
tine Republic, Bolivia, Peru, Guiana, and Columbia, are comprised in. this 
great meteorological region. The trade-wind, turned back under the 
equator in an east and west direction, ascends with a uniform force the 
valley of the Amazons, penetrates into the gorges of the Andes, and even 
crosses by all the defiles the higher barrier of mountains ; but sheltered 
by this enormous rampart the shores of the Pacific are not subjected to 
the influence of the east wind. The vessels which sail in the open sea 
have to traverse from one hundred and twenty-five to six hundred and 
twenty-five miles, according to the latitudes, before a gust of the trade- 
wind, descending from the summit of the Andes, comes to swell their sails 
and drive them to the coast of Australia. 

Even in those pafts of the world where the tropical winds cease to be 
permanent, the oscillations and deflections of the atmospheric current pre- 
sent in general a periodical character, and occur regularly, according to 
the course of the seasons. Among the regular return winds we may cite 
principally the " monsoons " of India and Arabia, The Arabian name for 
these meteoric phenomena, maussim, or tnousshn, signifies change, season ; 
it is because, in fact, they divide the y^r in the most exact manner into 
two totally distinct periods. During the great hgats of summer, the arid 
plateaux of Central Asia, and even the plains of Hindoostan, much more 
heated than the sea, act like a great respiring pump ; the air which rests 
above this part of the Asiatic continent expands, and in consequence new 
aerial masses flow without cessation from the Indian Ocean to the coun- 
tries on the north. According to Dove, the trade-wind of the south-east, 
carried away by this general displacement of the air, would itself cross^^ 
the equator, enter into the northei'n hemisphere, and transform itself grad^^^ 
ually into a monsoon from the south-west, because of the great speed it 
acquires at the equator. Still it is not probable that it is so, for the mon- 
soon has not the same vertical height as the trade-winds, and its direction 
is not uniformly from south-west to north-east, as on the coasts of Mala- 
bar ; in the valley of Scinde and in that of the Irrawaddy it is directly 
south ; at the extremity of the Gulf of Bengal, at Siam, at the eastern an- 
gle of the Asiatic continent, its direction is from south-east to north-west, 
perpendicular to the coasts which attract the wind.* 

Saturated with the moisture which has evaporated from the great cal- 
dron of the Indian Ocean, the monsoon inundates the coasts of Malabar 
with torrents of rain, deluges the shores of the transgangetic peninsula, 
* Miihry, Zeitschrift fiir Meteorologie von Carl Jelinek, No. 21, 1867. 



THE MONSOONS. 237 

find then strikes against the high raoimtains of the Himalaya, and other 
chains, which border the plateaux of Central Asia on the south, but it does 
not cross this barrier. By its clouds charged w.ith rain, which are rent 
by the escarpments of the inferior peaks, we see clearly that the sea-wind 
does not pass the altitude of 4950 to 8250 feet, and that above it another 
aerial stratum is moving in the heights. The movement which carries 
along this elevated stratum is the same as that of the monsoon from the 
south-west; but we recognize by its long trains of c^m, from 16,ft00 to 
25,500 feet high, that great returning current, or counter trade-wind, that 
blows at the same elevation above the Atlantic in the neighborhood of 
the Canaries. 

When the sun, in its course over the ecliptic, returns toward the Tropic 
of Capricorn, the centre of attraction is at the same time displaced in a 
southerly direction. The monsoon of the south-west ceases to tend to- 
ward the great peninsulas of Asia, the regular wind from the north-east 
recommences to blow, and the currents of attraction in the southern hemi- 
sphere turn back toward the islands of Sunda and Australia. Owing to 
this regular alternation, which was a surprise to the ancient Greek navi- 
gator Hippalos, the mariners of the Indian Ocean may count beforehand 
on a favorable wind which by turns will drive their ship before it for the 
two passages, going and returning ; and they have not to dread those pro- 
longed calms which are the bane of sailing vessels in the equatorial zone 
of the Atlantic and the South Sea. The circulatory system does not in 
any place pass beyond the lower strata of the aerial ocean, and we may 
easily perceive above the islands of Sunda and i^ustralia, as well as over 
the sides of the Himalayas, the constant progress of the clouds which are 
brought by the regular trade-winds. A volcano of Java, observed by 
Junghuhn, affords a remarkable example of this. From its summit, about 
9900 feet high, a column of vapor, escapes all the year round, which bends 
gracefully in space, and directs itself toward the west, or north-west, in a 
long whitish cloud, and it is in precisely the opposite direction that the 
monsoon blows during six months of the year, on the slopes as well as at 
the foot of the mountains. 

The monsoons of the East Indies are not the only winds which break 
the uniformity of the trade-winds. In all those parts of the tropical zone 
where the shores of the continents are disposed parallel to the equator, 
the winds alternate regularly, in consequence of the greater rarefaction of 
the air, which occurs now on the earth, now on the sea, according to the 
position of the sun. Thus, during the greater part of the year, the Afri- 
can coasts, which stretch from the Bight of Benin to Cape Palmas, attract 
the monsoons of the Gulf of Guinea. These masses of air changing their 
direction, turn back to blow in a north-easterly direction, and rush rapid- 
ly toward the great furnace or the Sahara, where the overheated atmos- 
phere is usually more expanded than in any other country of the world. 
Toward the month of January, when the Sahara itself has become colder 
than the equatorial seas and the banks of the Congo, the trade-wind of 



238 



THE ATMOSPEEBE AND METEOROLOGY. 



the north-east re-assumes the supremacy, and traverses the whole of 
Northern Africa obliquely to the south, toward the coasts of Southern 
Guinea. Very violent ^t first, it soon becomes weaker, and hardly lasts 
) but two or three weeks, when it again gives place to the marine monsoon. 
During its short prevalence the current coming from the desert does not 
cease to bring with it a white dust having the appearance of a thick fog. 
It is the sand of the Sahara, which in the regions situated immediately to 
the ncfrth of Guinea is almost white, while farther the dust raised from 
the ground by the Harmattan is nearly red.* 




Fig. 107.— Trade-winds and Monsoons of the Atlantic. 

On the coasts of Chili, on those of California, in the islands of the 
Pacific, around the Gulf of Mexico and the sea of the Antilles, analogous 
phenomena occur. In summer the valley of the Mississippi and the pla- 
teaux of Texas are traversed by real monsoons, which distribute the rain 
over that part of the continent, and then are in turn replaced by those 
dangerous winds from the north or north-east (nortes), which are them- 
selves trade-winds, more or less turned aside from their route. On their 
side, the western shores of Mexico present a similar alternation of winds, 
those from the south-west coming in summer, and those from the north- 
east in winter. On coasts parallel or merely oblique to the path of the 
trade-winds, a part of these winds is not" brought back, as in the West 
Indies or at Guinea, but it is more or less attracted by the centre of heat, 
which lies out of its regular course. It is t^ius that on the coast of Mo- 
* Borgbero, Bulletin de la Society Geographic, July, 1866. 



ETESIAN WINDS. 239 

rocco, and near the archipelago of the Canary Islands, the wind from the 
north-east is subject to a considerable deviation toward the African con- 
tinent, and is sometimes transformed into a wind from the north. In the 
same way the plateaux of New Granada and the llanos of Venezuela turn 
aside the normal current which penetrates into the sea of the Antilles, 
and oblige it to blow perpendicularly to the coast. Thus a periodical 
breeze {los hrisotes) is produced, which may be considered as an interme- 
diate wind between the monsoon and the trade-wind properly so called. 

The winds of the Eastern Mediterranean, to which the ancients gave 
the name of Etesian winds (from e?05, yeai"), are also nothing else than 
monsoons. These are atmospheric currents drawn from the north toward 
the continent of Africa, by the powerful centres of attraction formed by 
the sands of Egypt and the Sahara. During nearly the whole summer 
the aerial masses which repose above Southern Europe are thus carried 
away to the coasts of Africa ; and even in temperate countries with vari- 
able winds, like Italy, Provence, and Spain, it is affirmed that the predom- 
inating currents are those from the north. Owing to this general move- 
merit of the air, the passage from Europe to Africa is accomplished, on an 
average, more I'apidly than the returning voyage ; for the sailing vessels, 
which traverse the Mediterranean between France and Algiers, the pas- 
sage from the north to the south is about a quarter less than the route in 
the opposite direction. All the northern part of the Balearic Islands, and 
especially of Minorca, is laid waste by a wind from the north, which 
stunts vegetation, and causes all the trees to lean in a southerly direction.* 
* Marie-Davy, Lts Moiivements de V Atmosphere et des Mers. 



240 THE ATMOSPHERE AND METEOROLOGY. 



CHAPTER VII. 

LAND AND SEA BREEZES. — WINDS FEOM THE MOUNTAINS. — SOLAR BREEZES. 
— LOCAL WINDS. — THE SIMOON, SIROCCO, ECEHN, TEMPESTS, AND MISTRAL. 

Besides the lateral deviations which occur twice in the year, the trade- 
winds are subject along the coasts to rapid daily deviations. The whole 
outline of the continents is bordered, so to speak, with a fringe of breezes 
produced by the difference of temperature between the land and the wa- 
ter. During the day the countries of the coast-line are heated much more 
rapidly than the surface of the ocean. Toward ten o'clock in the morning, 
after a shorter or longer period of calm, a rupture of the equilibrium oc- 
curs between the aerial masses, and the fresher atmosphere reposing above 
the waters tends toward the land, there to replace the expended air which 
rises into the higher regions. Little by little this movement of transla- 
tion, which at first only made itself felt in the neighborhood of the coast, 
communicates itself to all the surrounding atmospheric strata, and soon 
the breeze moving nearer and nearer through the ocean of air, occupies a 
tolerably large space above the sea and the continent, which it unites as 
an iron plate unites the two branches of a magnet. During the night the 
ground loses by radiation a great part of the heat that it had received, 
while the sea preserves pretty nearly the temperature of the day. The 
equilibrium is again disturbed, but it is now in the direction of the sea ; 
the breeze is brought back, and blows in the opposite way. It is thus 
that in a space of twenty-four hours the breeze oscillates from land to sea, 
and from sea to land, by a motion of ebb and flow analogous to that of 
the tides. In the countries of La Plata these alternate breezes from land 
and sea present such a regularity that they have received the name of 
virazones (gyrations). Around Otaheite they also succeed each other 
with such punctuality that a vessel could for several consecutive nights 
make the tour of the island, and always with the wind behind it. 

These breezes, which one might also call daily monsoons, co-exist with 
the movement of the trade-winds, and are in consequence carried along in 
the general circuit. Instead of being at right angles to the coast, they 
more often form with it an acute angle ; they blow crossways, as Captain 
Dampier said. Nevertheless, it is not only in the domain of the trade- 
winds or along the borders of the ocean that the littoral breezes occur ; 
they blow everywhere where a considerable difference of temperature ex- 
ists between the land and the water, wher.ever the fresh air of the sea or 
of a lake goes to fill the vacuum left on the coast-line by an ascending 
current of warm air. A remai-kable example of it is seen in the narrow 
Adriatic Sea. There, during each fine day, the breeze rises in the centre 
of the gulf, and takes its direction at the same time in two contrary ways; 



LAND AND SEA BREEZES. 241 

on one side toward the shores of Italy, on the other toward the islands 
and mountains of Istria and Dalmatia, During the night the coasts 
that surround the waters of the Adriatic send back to the sea, as to a com- 
mon centre, the fresh air which they have received ; to the divergent cur- 
rents of the day succeeds a wave of convergent breezes. 

In the same way the mountains have their own system of breezes alter- 
nating with a regularity similar to that of the land and sea breeze on the 
coasts of the ocean. In the day, esj)ecially in summer, when the summits 
of the mountains are exposed to all the intensity of the solar rays, and re- 
ceive a considerable quantity of heat which causes their temperature to 
approach that of the valleys, the air reposing on the summits expands aflP 
rises. At the same time, the air of the plains which lie at the foot of the 
mountains is itself expanded in greater proportions, so that an ascend- 
ing current is produced from the base to the summit of the peaks, in all 
the valleys, and over all the escarpments. The atmospheric strata of the 
plain move in the direction of the heights with all the more impetuosity 
the more strongly heated the summits have been by the sun. In certain 
valleys, especially those of the Stura, and other Alpine rivers, which water 
the plains of Piedmont, the ascending wind has such force that the great- 
er part of the trees are uniformly inclined toward the mountains. Pol- 
len, remains of plants, insects and butterflies, are carried away by the 
current of air, and by their debris soil the whiteness of the snow. In the 
night, phenomena of an opposite kind are produced, but with less inten- 
sity ; the high mountains, whose summits rise far into the sky, lose their 
heat by nocturnal radiation more rapidly than the valleys, the sheets of 
air which surround them are chilled and descend again, in part toward 
the plains from which they had ascended a few hours before. Thus an ex- 
change between the two zones is established, an ebb and flow, a rising and 
falling atmospheric tide, regulated in its intensity by the variations of the 
temperature ; and here we see again, as in the coast breezes, the rotatory 
movement pointed out by Dove.* • 

As an example of these breezes, called in the French Alps j^ontias, re- 
hats, aloups du vent, we may cite the three aerial currents which flow in- 
cessantly in the valleys of Savoy, unless the local system of atmospheric 
currents be modified by tempests. These three streams of air are those 
of Faucigny, Tarentaise, and Maurienne. The first traverses the valley of 
the Arve from Geneva to Mont Blanc ; the second moves in the valleys 
of the Isere, and its tributary, the Doron ; the third alternately ascends 
and descends the valley of the Arc toward Mont Cenis and the pass of 
Iseran. Ordinarily, the ascending wind commences toward ten o'clock in 
the morning in the valleys of Savoy, and the descending current flows 
back again toward the plains at nine o'clock in the evening. In certain 
places, it is called matinihre, because it makes itself felt, mt)st of all, be- 
fore the rising of the sun. M. Fournet, who has for a long time studied 
these phenomena of atmospheric tides, has ascertained that the passage, 
from the ebb to the flow, is especially rapid in the narrow defiles, while 

16 



242 THE ATMOSPHERE AND METEOROLOGY. 

in the large basins the alternation is produced after a series of aerial os- 
cillations, and gusts of wind in the opposite direction. Each valley owes 
a special atmospheric condition to its particular form ; in one, the success- 
ive breezes are slow and undecided in their pace; in another, they alter- 
nate abruptly, and with violence, producing in the space of a few hours 
variations of temperature of thirty-five, forty-five, and even fifty-five de- 
grees. In general, the breezes are regular in the regular valleys, and only 
present remarkable peculiaiities at their issuing into the plain, or else at 
the confluence of two gorges. Among these winds with peculiar motions, 
a breeze of the Rhenish basin may be mentioned, known under the name 
tS^ihe Wisper-wind. Emerging above Lorch, from the narrow valley of 
the "Wisper, which is filled with woods, and so situated as to be subject 
in its difierent parts to all the extremes of temperature, this breeze gen- 
erally blows till eight, nine, or ten o'clock in the morning, then crosses the 
Rhine, strikes against the rocks of the left bank, and divides into two cur- 
rents, one of which re-ascends to the south toward Bingen, increasing it- 
self on the way by several small tributary winds ; while the other, which 
is weaker, descends to the north toward Bacharach. 

Even in the plains and countries but slightly varied in surface, daily 
breezes may succeed each other regularly, because of local difierences of 
temperature produced by the progress of the sun. In the morning, as 
soon as the sun rises, the temperature, which had fallen to its lowest be- 
cause of the nocturnal evaporation, increases rapidly, the air expands and 
spreads toward the colder spaces which extend on the side of the west ; 
a little wind from the east results from this, which becomes gradually a 
wind from the south-east, in proportion as the sun mounts above the ho- 
rizon. At noon the expanded air spreads in the direction of the north ; 
and finally, toward the evening, it is on the eastern side, where the aerial 
strata are chilled, that the surplus air, still heated by the solar rays, di- 
rects itself. Thus, when the atmosphere is not agitated by a general 
wind, a breeze turning regularly round the horizon in the same direction 
as the sun must be produced. * In the northern hemisphere this movement 
of gyration is accomplished from east to west by the south ; in the oppo- 
site hemisphere it is by the north that this diurnal breeze efiects its grad- 
ual revolution from east to west. In mountains the phenomenon is more 
complex, on account of the ascending and descending breezes, which are 
intermixed with the gyrating ones. It is remarked, however, that the 
greater part of the local winds, determined by the difierence of tempera- 
ture, tend toward the west in the morning, then turn gradually in an op- 
posite direction, and blow toward the east when the sun is sinking. These 
are the solaures {solis attra) or solar winds of the department of the Drome.* 

As to the local winds, which characterize certain regions, they origi- 
nate in the uwequal distribution of heat. Such are the chamsin of Egypt, 
the 'pampero of the Argentine Republic ; such, above all, is that aerial cur- 
rent to which the name of Simoon, or " poisonous," is given, in the Sahara. 
As soon as this wind commences to blow the panting traveler can scarce- 
* Fournet, Hydrologie du Rhone. 



THE SWISS ''FCEHNy 243 

]y breathe ; the air is burning and dried up, as if emerging from the mouth 
of an oven; the heat, increased by the radiation of iiuiumerable grains of 
sand which float in the atmosphere, rises rapidly to 113, 122, and even 133 
degrees Fahrenheit ; the sun is veiled, and every object assumes a violet 
or dark-red hue, while space is filled with dust. In order not to be smoth- 
ered by this irrespirable air, travelers must enveloj) their faces in their 
garments, and the camels bury their necks in the sand. But the simoon 
is not always accompanied by clouds of dust. Palgrave, who endured a 
violent simoon in the Desert of Arabia, saw not a single cloud of sand or 
vapor in the sky, and could not explain the sudden gloom which had in- 
vaded the atmosphere.* 

In Sicily and in the south of Italy a warm wind occasionally blows from 
the south, which is considered as a sort of simoon, and is saturated with 
moisture in passing over the Mediterranean ; this is the sirocco. Usually 
it is not very rapid, and its gusts are interrupted by stifling calms ; the 
surface of the water is hardly agitated, a mist of vapors broods on the ho- 
rizon, and the sun hides itself behind a veil of whitish clouds. Under the 
enervating influence of this wind from the south, all exertion becomes 
painful; but still the terrible phenomena, which occur during the simoon, 
have never to be dreaded. 

In the Alps of Switzerland the south wind is known under the name of 
foehn, a word derived from favonius, the southern wind of the Romans. 
What is, then, the origin of this current ? Has it originated in the Sahara, 
as Messrs. Desor, Martins, and Escher von der Linth beliqve, and has its 
burning breath first served to melt the apcient glaciers of the Alps ? Or 
is it simply a counter trade-wind descended from the heights of the at- 
mosphere, and does it come from the Atlantic and the Caribbean Sea, as 
Dove asserts ? Would not the moisture which it brings tend to enlarge 
the vast rivers of ice ? The latter seems probable ; but however it may 
be, the foehn frequently changes its course, and whether or not it is a con- 
tinuation of the Mediterranean sirocco, the inequalities in the relief of the 
mountains modify its character singularly. In rising over the slopes, the 
air expands more and more in consequence of the lesser atmospheric press- 
ure, and it loses a great quantity of heat ; from the warm wind, which it 
was at the foot of the mountain, the foehn becomes a cold current. The 
ridge once crossed, the aerial mass, which descends again toward the 
plains, is gradually compressed by the upper strata, and th^quantity of 
caloric, which had disappeai'ed because of the expansion, is reproduced , 
the cold wirfd of the summit is heated again to blow in the valleys. This 
is a remarkable phenomenon in the mountains which separate Valais from 
Piedmont and Lombardy. From being very warm at the entrance to the 
Italian gorges of the Alps, the atmospheric current from the south is 
cooled by from thirty-five to fifty-five degrees in passing over Mont Rosa ; 
it lets fall rain and snow in abundance ; then, after having descended 
again on the opposite slopes, it brings to the peasants of Switzerland 
something of the burning climate of the tropics.f 

* A Year's Travel in Central Arabia, 2 vols. f Helmholz, la Glace et les Glaciers. 



244 THE ATMOSPHERE AND METEOROLOGY. 

As to the fearful tempests or tourmentes which occasionally surprise the 
traveler on high mountains or in the snowy plains, they may result from 
winds blowing from almost any point of the horizon. It is a terrible 
thing to be assailed by one of these phenomena. The white masses car- 
ried by the gusts of wind hide all surrounding objects. The unhappy 
people lost in this storm see neither the neighboring slopes nor the sky 
above their heads, nor even the path beneath their feet. Deafened by 
the noise of the tempest, blinded by the powdery clouds which lash their 
faces, frozen by the snow which hangs in stalactites to their hair and 
changes their clothes into stiff and heavy masses, the travelers soon lose 
their way, and sink stupefied by the cold. Hundreds of corpses of men 
and horses, which have fallen here and there in certain passes of the Ka- 
rakorum and the Himalayas, recall these terrible snow-storms, which have 
prevailed over these mountains. Accidents of the same kind are very 
numerous, also, on the par/ocmos of India, Chili, Bolivia, and Peru. Even 
in the Pyrenees and the Alps, where the*tiost frequented passes are pro- 
vided with hospices, where travelers surprised by the whirlwind of snows 
may take refuge, many unfortunate persons perish every year in these 
tourmentes. 

The countries to the south of France have also to submit to the effects 
of a wind, which is a real scourge ; it is the wind from the north-west, 
to which popular imagination has given the name of " master " {mistral, 
magistraoii, maestrale). It is caused, like the alternate winds from the 
mountains, by the juxtaposition of two surfaces unequally heated. This 
aerial current is unhappily well named, for its speed, comparable sometimes 
to that of the hurricane, suffices to uproot trees and throw down walls. 
" The melamporeas" says Strabo, " is an impetuous and teri-ible wind, 
which displaces rocks, precijjitates men from their chariots, and strips 
them of their vestments and arms." The Gauls of the valley of the Rhone 
saw in it their most dreaded god ; they raised altars and offered sacrifices 
to it; 'the Provencals considered it with "Durance," and the "Parlia- 
ment" as one of their three great calamities. This wind makes itself es- 
pecially felt in winter and spring, when the Cevennes, covered with snow, 
have become relatively very cold, and the sea-shores continue to be heated 
daily by the rays of the sun : then the masses of air roll in volumes from 
the summit of the mountains, to replace the ascending current of the ex- 
panded atmosphere, which is formed above the region of the coast-line. 
During the night, it is true, the low lands situated at the base of the 
mountains lose their heat by radiation, and the afflux of cold air dimin- 
ishes, to recommence on the morrow, when the sun warms the atmosphere 
of the plains anew. In summer, the difference of temperature is less be- 
tween the shores and the desert escarpments of the Cevennes. The mis- 
tral is very feeble during this season, or it even entirely ceases. In vari- 
ous parts of the coasts of Spain, Jtaly, Greece, and Asia Minor, winds of 
the same kind, known under other names, descend in the same manner 
from the summit of the borderinsr mountains. 



ZONE OF VAMIABLE WINDS. 245 



CHAPTER VIII. 

^ONE OF VARIABLE WINDS. — STRUGGLE OF OPPOSING WINDS. — MEAN DI- 
RECTION OP THE ATMOSPHERIC CURRENTS. LAW OP GYRATION. 

Beyond the changing limits where the trade-winds of the two hemi- 
spheres blow, commence the zones of variable winds. There the masses 
of air flow now in one direction, now in another, and apparently in a very 
irregular fashion. Sometimes a single wind directs itself incessantly dur- 
ing whole weeks toward one point of the horizon ; sometimes the atmos- 
pheric currents which succeed each other make the tour of the compass 
in a few hours; at other times, again, the air remains calm between two 
meteorological regions where the winds move in opposite directions. In- 
deed, the word weather-cock has become a synonym of all that is unstable 
and versatile. 

That which contributes to this disorder of the air in Europe, and in the 
other lands which are outside the zone of the trade-windg, is the inequality 
of the ground. The general currents which pass above a chain of mount- 
ains do not blow with the same regularity as in the plain. In fact, the 
winds must be all the more unequal in their successive gusts, the less 
even the surface is over which they blow. The same wind, which moves 
over the seas with the uniformity of an immense river, departs from its 
regular pace as soon as it is interrupted in its course by inequalities 
of the Soil. At the foot of the grand mountains of Switzerland, and es- 
pecially in the environs of Geneva, where the surface relief is already very 
varied, the alternations which are produced in the force of the wind are 
such that the anemometer sometimes indicates a variation of intensity 
from single to triple. In the high gorges of the Alps it often happens, 
even during violent tempests, that the atmosphere presents at intervals 
the most perfect calm. To all the furies of the tempest there succeed for 
an instant silence and repose, then the hurricane recommences to blow 
with great violence. This is because the atmospheric cui'rents, similar in 
this respect to the rivers of the ocean, do not direct themselves invariably 
toward the same point of the horizon, and move by successive oscillations, 
now to the right, now to the left of the axis of their movement. In con- 
sequence, when we find ourselves placed on a point in the mountains 
which commands a view of the highest peaks, we must, according to the 
various directions which the aerial current takes, be by turns exposed to 
the fury of the tempest, or protected Jby some high summit on which the 
force of the wind is broken.* Even in countries but slightly varied in 
surface, or over plains covered with houses and woods, the wind does not 
blow in equal manner like the trade-wind of the seas. It advances by a 
* H. de Saussure, Voyages dans les Alpes. 



246 THE ATMOSPHERE, AND METEOBOLOaY. 

series of gusts and blasts, each one of which represents a victory of the 
atmospheric current over an obstacle on the plain. Close to the ground 
the wind is always intermittent, while in the heights of the air it proceeds 
almost always with an equal and majestic movement like the current of a 
river.. 

The abrupt gusts of the lower strata of this ocean are thus only second- 
ary phenomena, and in all the sudden turns of the winds, which one might 
easily believe to have occurred by chance, the disorder is more apparent 
than real. Though the wind makes itself felt by turns from every part 
of the horizon, there, nevertheless, exist only two atmospheric currents in 
each of the temperate zones — that which comes from the pole to replace 
the expanded air of tropical regions, and that which flows back from the 
equator after being raised in the heights of space above the stratum of 
the trade-winds. In the northern hemisphere these two winds set out, 
one from the north, the other from the south ; but in consequence of the 
rotatory movement of the earth, their direction is gradually changed, like 
that of the trade-winds. The wind from the north changes into a wind 
from the north-east, while the wind from the south ends by blowing from 
the south-east. Thus, as Dove remarks, the greater part of the aerial cur- 
rents deceive the observer, because they do not come from the regions 
whence they appear to blow. The wind from the north-east is in reality 
much more the wind from the north than the mass of air whose direction 
is truly southern ; in the same way, the wind from the south-east is truly 
the south wind, and that which seems to come from the south has the 
south-east as a starting-point. 

Two great aerial currents thus dispute the extent of each terrestrial 
hemisphere from the pole to one of the tropics. Generally, all this space 
is divided into vast oblique bands, composed of masses of air flowing in 
opposite ways, some from the pole, and others from the equatorial regions. 
The bands move over the circumference of the globe, and in the same 
space ; it is now the polar wind, and now the tropical wind which prevails. 
But a compensation never fails to be effected between these atmospheric 
currents, and the wind neutralized or repulsed in one part of the hemi- 
sphere soon makes itself felt at another point. While the strife exists be- 
tween two masses of air animated by contrary movements, the vicissi- 
tudes of the conflict and the gradual preponderance of one of the winds 
result in temporarily modifying the direction of the air, and making the 
weather-cock turn successively to the various points of the horizon. It is 
from the meeting of two regular winds that the ajjparent irregularity of 
all the atmospheric system results. 

Though the strife between the two aerial streams, now at one point, 
now at another, does not cease, tjiey are not, however, equal in force, 
and one of them always finishes by gaining the victory after a longer or 
shorter period of resistance. This wind of superior force is the returning 
current, descending from the heights of space to reach the level of the 
ground beyond the zone of the trade-winds. In fact, it is evident that in 



ATMOSPHERIC CURRENTS. 



247 



its circuit round the j^lanet any one stratum of air must be much more 
expanded when it repairs from the torrid zone to the frozen regions, than 
it is on its return from the pole, after having been condensed by the cold; 
it occupies thus, in consequence of its temperature, a^ much greater space 
in the first journey. This is not all ; the vapors with which the air of the 
equatorial zone is loaded contribute to expand it still more, while the 
polar winds are relatively dry, and, consequently, much more dense. Thus 
the winds which come from the tropical zone — that is to say, the south- 
west Avinds in the northern hemisphere, and those from the north-west in 
the southern hemisphere — must have the preponderance, and blow during 
a more considerable space of time. It is thus at least in the temperate 
zone of the north, where the winds which are directed toward the north- 
ern pole gain the victory, on an average, over the opposing winds. 



no^ 




America ddUorih 
EnSliivd 



Fig. 108.— General Direction of Winds in England and North America. The total duration of the at- 
mospheric currents for the year is represented by 100. 

As the atmospheric currents coming from the equator bend naturally 
toward the east, it follows that in the northern hemisphere most of the 
winds blow from the west. This is what we observe in North America, as 
well as in England. On the Atlantic coasts of France the proportion be- 
tween the winds which balance themselves around the western wind, and 
those which blow from directly contrary points of the horizon, is about 
three to two. The proportion would be much more ♦vorable to the for- 
mer if the chain of the Pyrenees, erected like a high barrier at the south 
of France, did not modify the direction of the atmospheric currents, and 
force them to make a detour by the Bay of Biscay, to bend again toward 
the east. At Cherbourg, in the open Channel, the difl:erence between the 
winds from the west and those from the east is much greater. Accord- 
ing to M. Liais, it is as seven to three. In the valley of the Saone and 
Rhone, the general movement of the winds is from north to south, as if 
the air were obliged to plunge in the kind of funnel formed by the Vos- 
ges, the Jura, and the Alps to the east ; the heights of the Cote d'Or, 
Beaujolais, and the Cevennes, to the west. It is the same with every sec- 
ondary valley. Thus the people of Valais scarcely know any winds but 
those from the east and west ; in the high valley of the Rhone, the only 
winds which make themselves felt are those from the north and south.* 

* Tschudi, Die Alpenwelt. 



248 THE ATMOSPHERE AND METEOROLOGY. 

According to Ktlratz, the mean direction of the wind in the whole of 
France is S. 88° W., that is to say, that the resultant of all the currents 
would blow from a point in the horizon situated at two degrees to the 
south of west. This direction of the wind explains perfectly why the 
large towns in France and the neighboring countries tend in general to 
increase on the side of the west ; they seek to breathe pure air. It is for 
this reason that the rich inhabitants of the great cities emigrate, from 
generation to generation, toward those portions of the suburbs which 
look toward the settina; sun. 




Fig. 109. — Map showing the general Direction of Winds in France. 

It is a remarkable fact, that the winds from the south-west increase in 
intensity in proportion as they approach the pole, while the winds from 
the north-east diminish gradually in force as they approach nearer the 
equator. The phenomenon is easily understood. The space traversed by 
the masses of air coming from the south is gradually restricted in the di- 
rection of the pole, and consequently the flow of the whole aerial river 
can not be effected save by an acceleration of speed. The polar winds, 
on their side, traverse latitudes where the sjDace opens wider and wider 



REGULAR GYRATION OF THE WIND. 249 

before them, and their force slackens gradually to the ti'opical zone, where 
they become the peaceful and regular currents of the trade-winds. 

Already, for some centuries, savants have ascertained that, in the north- 
ern hemisphere, the succession of the winds is accomplished in a normal 
manner in the direction from south-west to north-east by the west and 
north, and from the north-east to the south-west by the east and south ; 
this is a rotatory movement similar to that which the sun seems to de- 
scribe in the heavens, when, after having risen in the east, it proceeds to- 
ward the west, developing its vast curve around the zenith. Aristotle 
made this observation more than two thousand years ago in his " Meteor- 
ology:" "When a wind ceases to blow, and gives place to another wind 
of a neighboring direction, the change takes place according to the path 
of the sun." Since the time of the great Greek naturalist many authors, 
whom Dove has taken the trouble to enumerate, have re-affirmed this fact 
of the regular rotation of the winds, which was besides known to sailors 
from time immemorial. 

" When the wind veers against the sun, 
Trust it not, for back it will run," 

is a seaman's adage. Nevertheless, it is only in the nineteenth century 
that this meteorological phenomenon has been put beyond all doubt. 
Dove was the first to combine the scattered testimonies which confirm * 
the popular idea, and transform the ancient hypothesis into a scientific 
certainty. For the future, it has become an incontestable fact, thanks to 
the savant of Berlin, that in the northern hemisphere the winds succeed 
each other most frequently in a regular order, which is indicated by the 
following formula : 

S.W., W., N.W., K, N.E., K, S.E., S., S.W. 

In the southern hemisphere the normal rotation of the aerial currents is 
accomplished in the opposite direction — that is to say, from north-west to 
south-east by the west and south, and from the south-east to north-west 
by the east and north : 

N.W., W., S.W., S., S.E., E., N.E., N., N.W. 

Thus in each of the opposite hemispheres the procession of the winds 
coincides with the apparent path of the sun, which for Euroj^eans de- 
scribes its daily course to the south of the zenith, and for the Australians 
passes to the north of this same jDoint. Such is the regular order to 
which the discoverer has given the name of " law of gyration," and which , 
is often and very justly designated by the name of " Dove's law." Thus 
the general winds themselves follow, in their succession, the same order as 
the little diurnal breeze caused by the»relative position of the earth and 
the sun ;* and it is perhaps owing to the support of these light breezes 
that the normal condition of the rotation of the aerial currents is estab- 
lished in space. 

It is shown, by a great number of observations made in different parts 

* See above, p. 241. 



250 THE ATMOSPHEBE AND METEOROLOGY. 

of Europe, that the cortiplete revolutions of the winds in the normal direc- 
tion are much more numerous than those that occur in a retrograde direc- 
tion. At Liverpool, London, Brussels, and Kharkov, the direct revolutions 
constitute, on an average, two-thirds of the total revolutions ; in this re- 
pect, there is an almost perfect agreement between the atmospheric sys- 
tem of Western and that of Eastern Europe. In studying the partial revo- 
lutions, one does not always arrive at an analogous result, because the di- 
rection of an atmospheric cui'rent .often oscillates to the right and left of 
one point in the horizon before describing a complete rotation in one di- 
rection or the other. Nevertheless, in order to guard one's self against 
all errors, it is important to study assiduously all the oscillations of the 
weather-cock, for if such a complete gyration of the wind is not effected in 
the space of one month, the other kind can be completed in the space of 
a day. At Gnadenfeld, in Silesia, Kolbing observed a normal rotation, 
the duration of which did not exceed sixteen hours, which is the length 
of a winter night.* 

* Dove, Loi des Tempetes, p. 92 ; Poggendorff 's Annalen, Ixii. , p. 273, 



AERIAL EDDIES. 251 



BOOK IL— HURRICANES AND WHIRLWINDS. 



CHAPTER IX. 

AEEIAL 'EDDIES. — CYCLONES OF THE EQUATORIAL REGIONS. — THE "GREAT 

HURRICANE." 

It is nrobable that the wind is never propagated in a straight line. If 
it were, it would be because it did not meet, in its course, any salient 
13oints of the surface of the earth, nor strike against any other masses of 
air, either at rest or moving in opposite directions. The atmospheric cur- 
rents having always to strive against obstacles of this nature, must neces- 
sarily rebound to right or left, and advance by a series of eddies similar 
to those which the waters of a river form at the meeting of two currents. 
It is thus that a sudden wind raises the dust from the high-road, or drives 
before it the leaves of the forest. In the same way, during the winter 
days, when unequal breezes chase each other in the atmosphere, the flakes 
of snow, in descending, describe long spirals, and the smoke which rises 
unrolls itself in circles of an ever-increasing diameter. The particles of 
air, like the heavenly bodies themselves, revolve as they move.* If two 
gusts of air meet at the entrance of a valley, and are continued in long 
eddies, the circular movement is continued from place to place, like a 
wave on the surface of the water, and the entire aerial mass is disturbed 
in its equilibrium. 

In all the regions of the atmosphere, where two currents strike one 
another directly, or come in contact laterally, aerial eddies are instantly 
produced on the line of meeting, which move with extreme rapidity, 
and their vast whirls soon re-establish the equilibrium between the two 
masses of air. "When these eddies have only a local importance, they 
are known under the name of whirlwinds ; but when their effects are felt 
over a great extent of counti'y, the more general and more scientific des- 
ignation of cyclone, proposed by Piddington, is employed, "^lis term 
can be equally applied to the hurricanes (in Caribbean, aracan, kuiranvu- 
can) of the West Indies, to the tornadoes of the coasts of Africa, to the 
typhoons (ti-foong) of the Chinese Seas, to the revolving tempests of the 
Indian Ocean, and to the great gales of Western Europe. Still, we \)Ym- 
cipally designate by the name of cyclone those whirlwinds which are de- 
veloped according to a regular curve, either in the sea of the Antilles, or 
in the Indian Ocean, or more rarely in the Pacific Ocean. 

Meteorologists have ascertained that the revolving tempests of the 
* Carus, Natur undldee. 



252 THE ATMOSPHERE AND METEOROLOGY. 

equatorial regions occur especially at the time of the reversal of the reg- 
ular winds. Poey tells us that out of 365 hurricanes which have blown 
in the West Indies from 1493 to 1855, 245 (more than two-thirds) have 
taken place in October — that is to say, during the months when the 
strongly-heated coasts of South America began to attract toward them- 
selves the colder and. denser air of the northern continent.* In the In- 
dian Ocean it is principally toward the vernal equinox, at the time of the 
change of the monsoons, and after the great heat of the summer, that the 
cyclones are most numerous. In the list of hurricanes in the southern 
hemisphere drawn up by Piddington and completed by Bridet, not a sin- 
gle cyclone is mentioned for the months of July and August ; more than ^ 
three-fifths of these phenomena have taken place during the first three 
months of the year. It is at this epoch of the change of the se^^ons that 
the powerful aerial masses, charged with electricity, engage in strife for 
the supremacy, and by their encounter produce those great eddies which 
are developed in spirals across the seas and the continents. Still, the 
whirlwind never occupies in height more than a small part of the atmos- 
phere. According to Bridet, the mean height of the hurricanes of the 
Indian Ocean is rather less than two miles; and, according to Redfield, 
it is ver)'^ rare that a cyclone would prevail at the same time at the level 
of the sea and at more than a mile above it. Ordinarily the revolving 
stratum of air is much less thick ; occasionally it is even so thin that the 
sailors in a ship, whirled round by a cyclone, see above their heads the 
blue sky or the stars. Above this storm the winds follow their regular 
path. 

These sudden movements of the air are perhaps, after the great volcanic 
eruptions, the most terrible meteorological phenomena of our planet, and 
we can not be astonished that in the mythology of the Hindoos, Rudra, 
the chief of winds and storms, should have ended by becoming, under the 
name of Siva, the god of destruction and death. Some days before the 
terrible hurricane is unchained, nature, already gloomy and as if veiled, 
seems to anticipate a disaster. The little white clouds which float in the 
heights of air with the counter trade-winds are hidden under a yellowish 
or dirty-white vapor; the heavenly bodies are surrounded by vaguely 
iridescent halos and heavy layers of clouds, which in the evening present 
the most magnificent shades of purple and gold, stretching far over the 
horizon, iand the air is as stifling as if it came from the mouth of some 
great furnace. The cyclone, which already whirls in the upper regions, 
gradually approaches the surface of the ground or water. Torn frag- 
ments of reddish or black clouds are carried furiously along by the storm 
which plunges and hurries through space ; the column of mercury is wild- 
ly agitated in the barometer, and sinks rapidly ; the birds assemble, as if 
to take counsel, then, fly swiftly away, so as to escape the tempest that 
pursues them. Soon a dark mass shows itself in the threatening part of 
the sky ; this mass increases, and spreads itself out, gradually covering 
* Poey, Table Chronologique des Ouragans, etc., 1862. 



CTCLOXES IN THE TROPICS. 253 

the azui-e with a veil of a terrible darkness or a blood-colored hue. This 
is the cyclone which falls and takes possession of its empire, twisting^its 
immense sj^irals around the horizon. The roaring of the sea and skies 
succeeds to this awful silence. 

The progress of the wind experiences much more resistance in the in- 
terior of continents than on the seas; but the phenomena which are pro- 
duced there during, hurricanes are not less terrible. Buildings which oc- 
cur in the path of the storm are razed to their foundations, the waters of 
rivers are arrested and flow back toward their source, isolated trees are 
torn up and plough the earth with their roots, the forests bend as if they 
formed but a single mass, and give to- the tempest their broken branches 
and torn leaves. Even the grass is uprooted and swept from the ground. 
Innumerable fragments fly in the track of the hurricane like the waifs car- 
ried away by a fluvial or marine current.* Ordinarily, the action of elec- 
tricity is added to the violence of the air in movement, to increase the 
ravages of the tempest. Sometimes the flashes of lightning are so numer- 
ous that they fall in sheets like cascades of fire ; the clouds, and even the 
drops of rain, emit light ; the electric tension is so strong that sparks have 
been seen, says Reid, to dart spontaneously from the body of a negro. 
An entire forest in St. Vincent's Isle was destroyed without a single trunk 
having been overthrown. In the same way, on the shores of Lake Con- 
stance in Europe, a great number of trees which had remained upright in 
spite of the storm were completely stripped of their bark. 

It is principally on the shores of islands and continents where the tem- 
pest has not yet been retarded by the obstacles of the ground that the ef- 
fects of the storm are the most violent. It is there, too, that the greater 
number of human lives are destroyed in the general disaster ; for then the 
ships always repair to the ports, and in many places of the coasts there 
are low lands which the waters, suddenly rising, inundate to a vast isx- 
tent. Nevertheless, when the cyclone strikes against the mountains of a 
coast it can not surmount them, and the regions situated beyond remain 
completely sheltered. Thus in the island of Reunion the hurricane only 
strikes one side of the island at the same time ; too low to cross the 
mountains, it at first only devastates the plains situated on one side ; but 
in its mai'ch across the sea the wind doubles the promontory that arrested 
it, and the ravages are instantly recommenced. Since the time of Colum- 
bus, the first European who contemplated the hurricanes of the Antilles, 
thousands of ships have been swallowed up during the revolving tempests 
of the tropical seas, either in the depths of the ports and roads, or in the 
seas that bathe the coasts of America, China, Hindoostan, and the islands 
of the Indian Ocean. Such a cyclone as that of Calcutta in 1864, or of 
Havana in 1846, has shattered more than one hundred and fifty large ships 
in a few hours; such another catastrophe of the same kind, especially that 
which passed over the delta of the Ganges in October, 1737, drowned 
more than 20,000 persons in the rising waters. 

* Audubon, Birds of America. 



254 



TEE ATMOSPHERE AND METEOROLOGY. 




Fig. 110.— Calm during the hurricane at Reunion, February 15, 1S61. 



In the midst of the ocean the dangers which ships run are less than in 
badly inclosed roads of the coast; but the sensations experienced by the 
seamen must be all the more lively, by their being completely isolated 
and lost in the awful whirlwind. Around them the daylight is darkened, 
and darker than night one might say, since the little light that still re- 
mains serves only to show the gloom. The winds which howl and whis- 
tle, the waves which dash against each other, the masts bending and 
breaking, the groaning of the timbers of the ship, all these numberless 
sounds are mixed and confused in a terrible despairing wail, drowning 
even the peals of thunder. The sea no longer rolls in large and mighty 
waves, but boils over like an enormous caldron, heated by the fire of sub- 
marine volcanoes. The low clouds creeping above the waters often emit 
a lurid light that one would say was the reflection of some invisible Ge- 
henna ; at the zenith appears, surrounded by darkness, a whitish space 
which sailors have named "the eye of the tempest," as if they really saw 
a fierce god in the hurricane who descends from the sky to seize and de- 
stroy them. When, in the middle of this terrible storm, the sailors accept 



HUBRICANES AT REUNION. 



255 



~^~32oH 



H 



.#^' 







...i .J' 

55= 



Fig. HI.— Calm during the Hurricane at Reunion, February 17, 1T61. 

the strife with the elements, and, defying death, seek to manoeuvre and 
steer their dismantled ship without sails or masts, they certainly furnish 
a sublime example of human greatness. 

Among the effects that certain hurricanes have produced, there are sev- 
eral which would seem quite incredible, if the genius of man could not by 
means of powder and other fulminating matters impress on the air a still 
greater rapidity, and give it thus, though in very limited spaces, a force 
of destruction superior to that of the tempest. On the 26th of July, 1825, 
during the hmn-icane of Guada'loupe, a gust of wind seized a plank an inch 
thick and sent it through the trunk of a palm-tree sixteen inches thick. 
In the same way, in a lesser whirlwind which passed near Calcutta, a bam- 
boo was hurled through a wall of a yard and a half in thicl^ness ; that is 
to say, the breath of air in movement over this point had a force equal to 
that of a six-pounder.* At St. Thomas, in 1837, the fortress which de- 
fends the entrance of the port was demolished as if it had been bom- 
barded. Blocks of rock were torn from a depth of thirty or forty feet be- 
neath the sea and flung on shore. Elsewhere, solid houses, torn from their 
foundations, have glided over the ground as if flying before the tempest. 
On the banks of the Ganges, on the coasts of the Antilles, and at Charles- 
ton, vessels have been seen stranded far from the shore in open plains or 
* India Review. Dove, Loi des Teinpetes. 



256 THE ATMOSPHERE AND METEOROLOGY. 

in forests. In 1681, a vessel from Antigua was carried up the rocks three 
yards above the highest tides, and remained like a bridge between two 
points of rock. In 1825, at the time of the great hurricane of Guadaloupe, 
the vessels which were in the road of Basse Terre disappeared, and one of 
the captains happily escaping, recounted how his brig had been seized by 
the hurricane and lifted out of the water, so that he had, so to speak, 
" been shipwrecked in the air." Broken furniture, and a quantity of ruins 
from the houses of Guadaloupe, were transported to Montserrat over an 
arm of the sea fifty miles wide. From the mountains of St. Thomas the 
immense black whirlwind was seen from afar to pass across the sea and 
over the islands of Porto Rico and Santa Cruz. 

The most terrible cyclone of modern times is probably that of the 10th 
of October, 1780^-^yhich has been specially named "the great hurricane." 
Starting from Barbados, where neither trees nor dwellings M^ere left 
standing, it caused an English fleet anchored off St. Lucia to disappear, 
and completely ravaged this island, where 6000 persons were crushed un- 
der the riftns. After this, the whirlwind, tending toward Martinique, en- 
veloped a convoy of French transports, and sunk more than forty ships 
carrying 4000 soldiers ; on land, the towns of St. Pierre and other places 
were completely razed by the wind, and 9000 persons perished there. 
More to the north, Dominique, St. Eustatius, St. Vincent, and Porto Rico 
were likewise devastated, and most of the vessels which were on the path 
of the cyclone foundered, with all their crews. Beyond Porto Rico the 
tempest bent to the north-east, toward the Bermudas, and though its vio- 
lence had gradually diminished, it sunk several English war ships returning 
to Europe. At Barbados, where the cyclone had commenced its terrible 
spiral, the wind was unchained with such fury, that the inhabitants hid- 
den in the cellars did not hear their houses falling above their heads; 
they did not even feel the shocks of earthquake which, according to Rod- 
ney, accompanied the storm. The rage of man was arrested before that 
of nature. The French and English were then at war, and all the ships 
which the sea swallowed up were laden with soldiers seeking to destroy 
one another. At the sight of such ruin the hatred of the survivors was 
calmed. The governor of Martinique caused the English sailors, who 
had become his prisoners in consequence of the great shipwreck, to be 
set at liberty, declaring that in the common danger all men should feel 
as brothers. * 



iSPEED OF REVOLVING MASSEIS OF AIR. 257 



CHAPTER X. 

SPEED OF T^E REVOLVING MASSES OF AIR. — SPEED OF THE CYCLONE. — 

FALL OF THE BAROMETRIC COLUMN. IRREGULARITIES OF THE "WIND IN 

% THE PATH OP THE CYCLONE. 

It is not yet known what degree of swiftness the masses of air carried 
by the cyclones can attain, for it is in the upper regions of the atmos- 
phere, where the medium only offers a feeble resistance to the aerial cur- 
rents, that the storm-wind must have its greatest rapidity. And it does 
not suffice to ascertain the progress of the particles of air immediately 
at the level of the ground, or even slightly above it, to form an idea 
of the speed at which the atmospheric mass carried by the hurricane 
moves. In one of his ascents Mr. Coxwell made a journey of sixty-eight 
miles in sixty minutes, while below him the instruments indicated a speed 
of hardly fourteen miles in the same interval. Another time Mr. Glaisher 
moved at fifteen miles per hour, while at the Greenwich observatory the 
s%me sheet of air only advanced five hundred yards. How great, then, is 
the speed of the cyclone at a certain height above the ground, when on 
the earth, strewn with obstacles, it progresses at the rate of fifty yards per 
second, or one hundred miles per hour — four times the speed of our loco- 
motives ! This feai'ful rapidity of the air at the surface of the ocean, and 
the friction of the aerial particles which results, explains perfectly, as 
Cicero remarked 2000 years ago, why the temperature of the water rises 
.during storms.* 

As to the pressure exercised by the aerial current which moves with 
such speed, it is truly formidable. In a memoir on the construction of 
light-houses, Fresnel estimated the strongest pressure of the wind at six. 
hundred and sixteen pounds per square yard, but it is very probable that 
in a number of hurricanes this figure has been greatly surpassed. Not to 
mention the effects produced by the great cyclones of the tropics, a num- 
ber of cases have presented themselves in the temperate zone where the 
pressure exercised by the wind on a space of little extent was much great- 
er than meteorologists had foreseen. Thus, to cite but one example, the 
storm of the 27th of February, 1860, coming from the west, and plunging 
in the plain of Narbonne, by the strait where the canal and railroads of 
the south pass, was violent enough to force off the rails and partially 
overturn two trains, which it struck crossways, between the stations of 
Salces and Rivesaltes. According to the engineer, Mathieu, who proba- 
bly gives, it is true, too high an estimate, the pressure necessary to over- 
turn certain carriages must'have been nine hundred and fifty-two pounds 
per square yard of surface. f 

* De Ndtura Deorttm — Zeitschrift fiir Erdkunde, March, 1864. 
t Eugene Flachat, Traversee desAlpes. 

17- 



258 THE- ATMOSPHERE AND METEOROLOGY. 

The masses of air which revolve not far from the central part of the cy- 
clone are the only ones which attain the considerable speed of sixty and 
ninety miles per hour. As to the movement of the whole of the storm on 
the surface of the earth, it is naturally very slow in comparison to the cir- 
culatory movement of the aerial particles around their axis. The great- 
est speed of translation which has been observed is that of the hurricane 
in the month of August, 1853, which, after having advanced at the rate 
of twenty miles an hour from the Antilles to the Banks of Newfoundlan#, 
increased gradually in speed, and ended by exceeding fifty-six miles an 
hour. Most of the cyclones of the Antilles move, on an average, from 
twelve to eighteen miles in the same space of time ; but there are some 
too, especially among the typhoons of China, which advance so slowly 
that several writers have considered them as revolving on the same spot. 




Fig. 112.— Spirals made by the Vessel Charles Heddles. 

At the' end of the month of February, 1845, a hurricane which originated 
near the Mauritius traversed the Indian Ocean with an average speed 
above two miles per hour, while a ship, the Charles JETeddles, placed at 
about fifty-six miles from the axis of the storm, described immense spirals , 
around this changing point. In five days it made five complete revolu- 
tions in the midst of the sea, and though in this fantastic voyage it must 
at least have traversed 1500 miles, nevertheless, when it was finally deliv- 
ered from the grasp of the cyclone, it was only at four hundred and ten 
miles from the point of departure. The vessel had revolved like a top on 
the surface of the ocean. According to Bridet,* the speed of translation 
in the hurricanes of the Indian Ocean is comprised between the extremes 
of one mile and twenty miles an hour. 

The movement of the cyclone has the efiect of hollowing into a funnel 
all the central part of the whirlwind, and hurling the masses of air toward 
the cii'cumference of this enormous wheel which turns in the atmosphere. 
It is thus that in the rivers, and even the smallest tributaries, the eddies 
are always depressed in the centre, because of the centrifugal force which 
carries the waters along in a circle. The diminution of the aerial column 
makes itself instantly felt, by a corresponding diminution of weight, and 
the mercury sinks in consequence, as soon as the hurricane commences to 
be formed in the high regions of the atmosphere. The storm which is ap- 
proaching thus announces its proximity, and those whom it threatens can 
* Etude sur les Ouragans de I'Hemisphere Austral, 



ROTATION OF CYCLONES. 



259 



take their precautions so as to escape entirely from the disaster, or so as 
to diminish its effects. The sailors whose vessel is anchored in a sure 
port double their moorings ; those who are lying in an open road, exposed 
to the fury of the winds, as at Reunion, hasten to obey the signal gun, 
and fly to the open sea, so as to withdraw from the centre of the hurricane. 
The bai'ometer has been seen to fall by one and a half, two, and even two 
and three-quarter inches* — that is to say, nearly a tenth of the total height 
of the mercury, and each of these perturbations has not failed to be the 



s^ 



r 



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lllf 



^ 



6?" 



ser 



bt 




lilanritixis 





,J9° 



af 



^^ .•■ 



Centre of jOjEtcrricane 




53° 



S5" 



66° 



589 



2^ 



Fig. 113.— Cyclone in the Indian Ocean in January, 1852. 

signal of a storm all the more terrible the higher the barometer had pre- 
viously risen. At times the rarefaction of the atmosphere is accomplish- 
ed in such a sudden manner, that the air contained in the houses sudden- 
ly expands, explodes, so to say, and hurls windows and doors far away. 
For this reason, says Fitzroy, the habitations are left o^jen in certain 
places to avoid such accidents. 

In the sea, the waters rise to a greater or less height in consequence of 
the lessening of the atmospheric pressure, and move with the centre of the 
* On board the Duke of York^ in 1833, at the mouth of the Hooghly. 



260 



THE ATMOSPHERE AND METEOROLOGY. 



cyclone; thus a "tempest wave" is raised, whose force is added to that 
of the formidable surf which the wind has excited. This is the principal 
cause of those terrible tidal " races," no less dangerous than earthquakes, 
which roll over the neighboring coasts. During the hurricane of Barba- 
dos, in 1831, the waves which broke against the northern promontory of 
the island were seventy-two feet higher than the mean level of the water. 



l4»_ 



31" 






Eusricane ':^^- 

•> Great "breezes ;^a... 




^^•-"^^.. 
v.?^^ 



6i<> SI- 



hV .hh" 66° bl" 



Fig. 114. — Cyclone in the Indian Ocean in February, 1860. 

At the great cyclone of Calcutta, in October, 1864, the Hooghly rose 
twenty-two feet all along the lower part of its course, and inundated sev- 
eral islands. More recently still, in the great hurricane which devastated 
St. Thomas, a wave driven by the wind rushed over the small island of 
Tortola, committing such ravages that, according to an absurd legend, 
propagated by terror, the entire island was swallowed up. It is certain, 
too, that the water of the sea can be drawn in in greater or less quantitj^ 
by the vacuum which is formed in the midst of the whirlwind ; this has 



ROTATION OF CYCLONES. 



261 



occurred many times, and especially in Barbados. Reii^ saw showers of 
salt-water fall at a great distance from the shore in the interior of the isl- 
and, and destroy all the fresh-water fish in the lakes and streams. 

The circular movement of the cyclones does not occur indifferently in 
one direction or the other. ^Like the regular phenomena of the winds, 
these terrible storms, as well as all the other great atmospheric perturba- 
tions, conform to laws, and their progress can therefore always be foretold 
by sailors. In the northern hemisphere, the revolving storms of the trop- 
ics constantly blow from the south to the north by the east, and from the 
north to the south by the west ; in the southern hemisphere, the path 
taken by the whirlwinds is in the opposite direction, and the spirals of the 
wind are uniformly developed by the south, the west, the north, and the 
east. Such is the law discovered and brought to light by the labors of 







Fig. 115.— Parabola described by a Hurricane (after Bridet). 



262 THE ATMOSPHEBE AND METEOROLOGY. 

Reid, Redfield, ^iddington, Bridet, and other savants. Thus winds from 
all parts of the horizon blow at the same time round the circumference of 
the cyclone ; one ship is pursued by a furious wind from the east, while 
at fifty miles distant another vessel is sunk by gales coming from the 
west. And during all these tumults of warring elements, it sometimes 
happens that at the very centre of the hurricane the atmosphere remains 
perfectly calm ; a terrible peace, a formidable silence, reigns in the chang- 
ing circle formed by the raging whirlwind of the tempest. 

If the cyclone turned round in its place, the wind would blow exactly 
in the direction of the tangent over the whole course of the storm; but it 
is not thus because of the double movement of the hurricane ; while re- 
volving it moves on, and consequently the direction of the wind must be 
the result of the two forces which bear it along. Let the entire whirl- 
wind be directed toward the west, and the normal speed of the wind of 
the tempest, which blows in the same direction over the periphery of the 
cyclone, will be augmented by the speed of the storm itself In return, the 
wind which will blow toward the east will be partially neutralized, and 
along all the outline of the circle the direction and the speed will be mod- 
ified according to proportions rigorously established by calculation. These 
are the modifications to which the successive winds along the outline of 
the tempest are subject, and which often render the cyclones difiicult to 
recognize in the regions of the temperate zone, where the speed of rota- 
tion of the storms is considerably diminished. Under the ti'opics, where 
the whirlwind, being still restricted, is in its pi-imitive force, we remark 
the less this inequality of these partial winds of the hurricane. It is, how- 
ever, important enough to be recognized by mariners. One half of the 
disk of the tempest is called by them " dangerous semicircle," and the 
other "manageable semicircle." Now this part of the hurricane, which 
the great violence of the winds renders dangerous, is always found on the 
side of the cyclone where the wind proceeds in the same direction as the 
storm. That half of the disk where the wind adds its own speed to that 
of the movement of translation is, in the northern hemisphere, to the right 
of the trajectory of the revolving circle ; in the southern hemisphere, it is 
to the left.* The figure on page 261 gives an idea of the contrast which 
occurs between the two sides of the hurricane on the path that it trav- 
erses in the Indian Ocean. 

* Marie Davy, Mouvements de V Atmosphere et des Mers. 



SPIRAL OF THE HURRICANE. 263 



CHAPTER XL 

SPIRAL OF THE HURRICANES IN THE TWO HEMISPHERES. — THEORY OF CY- 
CLONES. — NAUTICAL INSTRUCTIONS TO AVOID HURRICANES. 

At their departure from tbe tropical regions, where they fell into col- 
lision with the trade-winds, or the monsoons, the greater part of the cy- 
clones of the New World proceed first toward the north-west, parallel to 
the line of the Antilles, or else along the shores of Columbia and Central 
America ; then, turning back, like a billiard-ball that rebounds in the op- 
posite direction from the impulse received, they follow the coast-line of 
the United States, describing in the air an orbit corresponding with the 
course of the Gulf Stream. 

In the southern hemisphere the phenomenon is inverted ; the cyclones 
of the Indian Ocean take their origin to the south of Hindoostan, and 
move to the south-west toward Reunion, Mauritius, and Madagascai-, then 
turn abruptly in a south-westerly direction toward the Antarctic seas. 
The spiral movement of the wind in this great tourbillon is effected from 
west to east by the north — that is to say, in the same direction as the hand 
of a watch. The movement is opposite to that which is taken by the 
hurricanes of the northern hemisphere. 

What is the cause of the cyclone itself, and whence comes this sudden 
change, which occurs in its direction toward the exterior limit of the trade- 
winds? According to Dove, this is the explanation of these phenomena: 

When enormous quantities of warm air ascend over the deserts of Asia 
and Africa, these expanded aerial masses must spread laterally. Those 
which are carried over the North Atlantic in a westerly direction, con- 
trary to that of the earth's movement, meet the returning current, which 
flows from the south-west to the north-east, in the opposite direction of 
the trade-winds. From this results a conflict between the two atmos- 
pheric currents ; a whirlwind of air is propagated in spirals in the north- 
westerly direction, which is the result of the two fo.rces at issue. At the 
same time, the revolving mass descends obliquely toward the surface of 
the sea, and being compressed to the right by the trade-winds, it con- 
tinues to advance toward the north-west. Arriving outside the tropics, 
the hurricane is no longer under the lateral pressure of the north-east 
wind ; it has a free path before it, and, under the influence of the earth's 
rotation, it bends with a graceful curve in a northerly direction, then in 
that of the north-east. At the same time, the storm which has just en- 
tered the temperate zone gradually enlarges the diameter of its spirals, 
and consequently loses its violence in proportion as it advances toward 
the pole. Thus the hurricane of 1839, whose breadth was about three 
hundred miles when it crossed the Antilles, extended to five hundred 



264 



TEE ATMOSPHERE AND METEOROLOGY. 



miles above the sea of the Bermuda^, and about the fiftieth degree of 
north latitude it did not occupy a space less than 1750 miles, but at the 
same time its destructive efiects diminished in proportion to its expan- 
sion. 

The same wind, which has just razed a town in the Antilles, and broken 
ships like playthings, sometimes contents itself, when it arrives at the 
Irish coasts, with uprooting a few trees and overturning some already 
tremblinsf rocks. 




Fig. 116.— SimultaneoTis Cyclones experienced at E^nnion, December, 1824. 

Such is the theory proposed by Dove, and which seems the most proba- 
ble, at least, for the hurricanes of the Atlantic. As to the cyclones of the 
Indian Ocean, they are, perhaps, produced by the conflict of the south- 
easterly trade-winds and the monsoon, which tends toward the continent 
of Africa. M. Bridet sees in them only the result of the meeting of two 



■i[„, (),.,,;,„ a:.- hurricane of august & September 1848. pi..xiii. 



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• THEORY OF CYCLONES. 266 

winds, one from the equator, the other from the southern hemisphere. 
That from the equator, participating in the great angular speed of this 
part of the globe, deviates toward the east, in proportion as it advances 
toward the Tropic of Capricorn ; the south Avind, carried less rapidly 
around the earth, deviates, on the contrary, toward the west ; and from 
these two deviations in opposite directions there results, at the meeting 
of the winds, a revolving movement in the direction from east to west 
by the south. On an average, the cyclones of the Indian Ocean have a 
diameter of from 250 to 300 miles in the commencement of their course, 
from 430 to 560 miles toward the middle, and from 560 to 700 toward the 
end ; their influence is sometimes felt as far as 1200 miles from the 
axis of the storm. It is true that two or more cyclones often follow one 
another at a little distance ; lateral eddies accompany the principal whirl- 
wind in the same way as occurs on the surface of the sea; besides«the great 
revolving funnel, formed by the meeting of contrary waters, many circles 
of the second order are hollowed out. Bridet has collected numerous ex- 
amples of these simultaneous cyclones.* 

Local obstacles, such as plateaux and mountain chains, may likewise 
cause hurricanes, when the aerial masses dash directly against them. 
Thus, in the Bay of Bengal, at the time of the change from the north-east 
to the south-west monsoon, the latter strikes against the mountains of Ar- 
racan, and in consequence of this shock a sudden cyclone occurs, which 
turns back toward the noi-th-west, and traverses the whole of Bengal and 
the northern provinces of Hindoostan as far as the Hindoo-Koosh. It is 
possible that the typhoons of the Chinese sea owe their origin to similar 
causes ; m this case they would be nothing else than deviating monsoons, 
transformed into hurricanes, because of the.obstacles opposed to them by 
the mountains of the Philippines and Formosa. Besides, all these hilly 
countries of diiFerent sizes and forms, which are scattered over that part 
of the Pacific Ocean, and are separated from on^ another by unequal and 
tortuous straits, can not fail greatly to disturb the normal condition of 
the winds,f and to produce a great number of storms and hurricanes often 
confounded under the general name of typhoons. On the other hand, on 
the Eastern Pacific, where the trade-winds blow with so much regularity, 
hurricanes, properly so called, are very rare. They have only i been ob- 
served on the eastern coasts of Mexico. 

While the cyclone develops its vast curves in the equatorial regions, 
the entire whirlwind must lean forward ; for the upper strata, carried away 
in the hurricane, find much less resistance in the air than the lower strata 
find above the ground, and the surface of the sea. The Avhole of the storm 
may, therefore, be compared to an immense wheel, revolving horizontally 
over the globe, and pressing the earth most strongly with its anterior 
part. Nevertheless, in extending themselves in large spirals in the two 
temperate zones of the north and south, the hurricanes become gradually 
subject to such modifications in opposite directions, and present apparent 
* Etude sur les Ouragans de V Hemisphere Austral. t See above, p. 237. 



266 



THE ATMOSPHERE AND METEOROLOGY. 



irregularities so considerable that they seem at first to obey other laws. 
Instead of leaning forward, one would say, on the contrary, that a real 
vacuum, incessantly enlarging, was opened on this side of the whirlwind. 



K 




Fig. IIT.— Dii-ection of Cyclones on the Surface of the Earth. 

Thus, as is proved by more than 300,000 observations made in the N"ortli 
Atlantic, on board American, English, and Dutch ships, and carefully com- 
pared by Messrs. Andrau and Van Asperen,* the winds from the north, 
* De Wet der Stromen, 1862. 



HOW TO AVOID HUEEICANES. 267 

which have passed the thirtieth degree of north latitude, arc almost al- 
ways wanting in the spirals of cyclones. In proportion as the meteor is 
developed toward the pole, the tranquil zone of the hurricane increases. 
The winds from the south and from the east diminish by degrees in fre- 
quency and in intensity ; they then disappear completely. Finally, from 
the fiftieth to the sixtieth degree of latitude, the rotation of the cyclone 
is represented only by winds from the north-west, west, and south-west. 
One might say that only half the hurricane remains. To the south of the 
equator, similar phenomena occur in inverse order, and every successive 
curve in the spiral of the storms presents in its southern convexity a 
greater or smaller break, according to the height of latitude. Fig. 117 
may explain the modifications which the cyclones experience while proceed- 
ing from the tropical regions toward the poles severally.* 

The fact that in the northern hemisphere the partial winds of the hurri- 
cane are always stronger on the right side of its path, and in the southern 
hemisphere always stronger on the left, is not sufiicient to explain this 
astonishing contrast between the two halves of the disk of the cyclone. 
M. Andrau and other Dutch savants have attempted to explain this ap- 
parent anomaly. Taken altogether, the hurricane may be considered, 
they say, as a disk revolving rapidly around its axis. Its natural tend- 
ency is to move incessantly in the same plane of rotation, and only the 
intervention of considerable force can make it incline in one or the other 
direction. It is true that at the point where' it originates over the equa- 
torial seas the cyclone leans more or less sti'ongly toward its source ; but 
in proportion as it moves toward the pole revolving round an imaginary 
axis that remains always parallel to itself, it must necessarily lean more 
and more backward, in consequence of the curvature of the globe. While 
the southern part of the hurricane still sweeps over the waves or the 
plains, the other part rises gradually to a great height in the atmosphere. 
Soon the upper winds of the tempest no longer make themselves felt at 
the level of the soil, and are only indicated by the fall of the barometric 
column and by the clouds which we see hurrying after each other at a 
great height in the sky. Toward the fiftieth degree of latitude to the 
north o» soutl; of the equator, the cyclones elevated half way only touch 
the earth by the winds of their lower extremity. These winds are the 
same in the two hemispheres ; they blow equally from the north-west, west, 
and south-west ; but on each side the gyration is accomplished in the op- 
posite direction. 

Piddington, Redfield, Bridet, Lartigue, and other learned meteorologists 
have drawn up rules of general conduct for mariners surprised by hurri- 
canes, which, when they are followed in time, may save the threatened 
ship. Warned by the barometer of the approach of the cyclone, the cap- 
tain must be very careful not to fly at full speed before the storm, in the 
vain hope of escaping the danger. By proceeding in this way, as terror 
would counsel him, he would rush precisely into the midst of the tempest, 
* Mittheilungen von Petermann, t. xi., 1862. 



268 THE ATMOSPHERE AND METEOROLOGY. 

and expose his ship to all the fury of the wind and the surf. To escape 
its violence, he ought to manoeuvre so as to tend obliquely toward the 
circumference of the storm as far as possible from the central part, where 
the Avind blows with all its force. Unhappily, whatever may be the sci- 
ence of the seaman and his knowledge of the seas which he navigates, it 
is often very difficult for him to know beforehand from which side the 
winds will approach, and what is exactly the orbit which the centre of 
the cyclone follows across the seas. Nevertheless, if he hesitates too long, 
he may suddenly find himself within the fatal circle, and be lost with his 
ship, from having lacked the necessary boldness. In the high latitudes 
of ocean it is easier to make a decision and escape from the cyclone, since 
the sea is open in the direction of the pole, and the sailor has not to dread 
being completely inclosed in the midst of a cirlcle of tempests. It is be- 
hind him that the lower part of the immense wheel ploughs the waves ; 
before him the ocean is open, or at least the winds which traverse its sur- 
face are produced by local causes, and do not belong to the terrible storm. 
Only at very rare intervals is the upper part of the cyclone brought down 
to the surface of the water by violent atmospheric counter-currents com- 
ing from the polar regions. In thirteen years the Dutch savants have 
only observed two cases of this nature. 

Thus the hurricanes themselves, like the other manifestations of life on 
our globe, have a regular course, and mathematicians can attempt to cal- 
culate the orbit of these terrible phenomena over the face of the earth. 
It is by conforming to laws, and following spirals traced beforehand, that 
the revolving tempests are propelled from the equinoctial zone to the 
temperate regions. Far from causing by theii* violent spirals a perma- 
nent disturbance in the air, they, on the contrary, only re-establish the 
equilibrium between the unequal waves of the atmospheric ocean. Still 
more, they aid, conjointly with the monsoons and the counter trade-winds, 
to maintain the astronomical equilibrium of the planet. Thus, as Dove 
remarks, the continual friction of the trade- winds, which the terrestrial ro- 
tation causes to deviate incessantly toward the west, would doubtless end 
by retarding the movement of the earth around its axis, if other aerial 
currents proceeding in afh opposite direction did not counterbalance the 
retarding causes, and accelerate on their part the rotation of the earth 
from west to east. Slight as may be the breath of wind compared to the 
force of projection which causes the planet to revolve, it does not the less 
contribute to the movements of the globe and to its harmonious circles in 
the concert of the heavenly bodies. 



EDDIES OF TEMPESTS. 



269 



CHAPTER XII, 

^ EDDIES OF TEMPESTS. WHIELWINDS. 

The atmospheric movements, called tempests or gales by seamen, diflfer 
from the cyclones by their slighter intensity, but are more numerous. In 
certain parts of the ocean, especially in the North Atlantic, they are so 
frequent, that during some months of the year we may expect a tempest 
once every two days. This is shown by the accompanying map, every 
rectangle of which indicates the number of tempests by a difierent tint. 



us So ^S 70 b'i Wo- ■fJ' So i, 



:> f» S 10 




SS fio jS yo es ,fio 5S •So i6 jo JS 3a 



tij..iS 36.i,o 3i.35 iS.zo z6.3q £x-23 u.jJ &^io S 

Fig. lis.— Tempests of the North Atlantic in December, January, and February. 

All these gales are propagated in spirals analogous to those of the hurri- 
canes. Storms of winter or tempests of summer originate to the right or 
left of the Gulf Stream, and are developed in gyrations, caused by the 
movement of the earth itself* There are likewise local cyclones, revolv- 
ing only over a single country like France or England, or even in a single 
valley ; we might cite numerous examples of similar tempests which in a 
limited space have been scarcely less destructive than the hurricanes of 
* Sonrel, Nouvelles Meteorologiques, March, 1 868. 



270 



THE ATMOSPHERE AND METEOROLOGY. 



the Antilles.* Often, when we contemplate the sky above our heads, we 
see clouds whirling under the influence of two hostile currents, and ap- 
proaching one another only to withdraw again. * But it is principally by 
ascending the side of a mountain that one can witness the curious sight 
presented by the conflict of two masses of air, which dive into a valley 
and describe a more or less rapid eddy with their clouds or mists. From 
the top of the headlands of the Pyrenees the meteorologist Lavtigue has 
observed a great number of these circular winds, similar to the circles 
which the water of a river describes above a rock.f 




Fig. 119. — Storm in the Pyrenees (after Lartigue). 

As to whirlwinds, properly so called, they are phenomena of small im- 
portance compared to the cyclones ; but, like them, they are due to the 
encounter of two, more or less considerable, masses of air, which strike 
against each other obliquely. Still, they do not turn invariably in one di- 
rection for each hemisphere, for they are not caused, like the hurricanes, 
by the strife of two regular winds, but may arise from the conflict of all 
the currents of air, either normal or variable, which traverse the surface 
of the earth. Observers have seen in the same regions whirlwinds which 

* Fitzroy, Weather-hooh. 

t Lartigue, Essai sur les Ouragans et les Ternpetes. 



HURRICANE OF MONVILLE. 



271 



revolve from the north to the south, some passing by the west, and others 
by the east. During a tempest there may even form on each side of the 
atmospheric current, as on the shores of a fluvial current, a series of ed- 
dies revolving in the contrary direction, and sometimes with sufficient 
speed to deserve the name of whirlwinds. In the full whirl of the cy- 
clone, the shock of the gusts of wind must likewise produce secondary ed- 
dies, moving with extreme speed, now in one direction, now in another. 




Fig. 120.— Storm in the Pyrenees (after Lartigne). 

If it were not so, we should not be able to understand how in the very 
centre of the hurricane the effects produced by the wind differ in so re- 
markable a manner in a space of small extent. Thus, according to Reid, 
it has often been ascertained that during the cyclones of Mauritius lofty 
houses half in ruins already were not even shaken by the storm, while 
solid buildings beside them were completely overthrown and destroyed.* 
Isolated whirlwinds are sometimes propagated yeith a rapidity as great 
as that of the hurricanes, and may cause similar disasters. The whirl- 
wind which passed over Malaunay and Monville on the 19th of August, 
1845, was not more than thirty-three to forty-four yards wide in certain 
places, and in its greatest breadth it hardly attained the third of a mile ; 
* Lartigue, Essai sur les Ouragans et les Tempetes, p.. 89. 



272 



THE ATMOSPHISBE AND METEOBOLOQY. 



notwithstanding which it committed the most terrible ravages, and the 
inhabitants of that part of Normandy long preserved the fearful memory 
of it. About one o'clock in the afternoon, after an oppressive day, during 




Fig. 121. — Hurricane of Monville. 



which the barometric column had suddenly fallen from 29*9 to 27"8 inches, 
some sailors saw the whirlwind forming over the Seine at the foot of the 
high cliffs of Canteleu. Like an inverted pyramid, blackish at the base 



WEIBLWmJDS OF BUST. 273 

and red at the summit, the whirlwind swept the waters with its point and 
then rushed into the valley of Maromme. It did not advance in a straight 
line, nor by elongated curves, but by abrupt deviations to right and left, 
like the zigzag of lightning. Through the woods which were on its path, 
it traced wide roads over trees overthrown, shattered, and reduced to 
ruin ; then approaching successively three gi-eat silk manufactories of 
Monville, it twisted them in its spirals, and struck and destroyed them. 
After having heaped up all these ruins, under which perished hundreds 
of workmen, the whirlwind opened an averftie in the ruins on the plateau 
of Cleres, then divided into two branches and ascended into space, carry- 
ing with it all kinds of objects, planks, slates, and papers, which fell down 
again near Dieppe at distances varying from fifteen to twenty-four miles 
from the place of the catastrophe.* It is evident, according to all ac- 
counts, that electricity played a very great part in the whirlwind of Mon- 
ville. 

These phenomena, as we can understand, produce different effects ac- 
cording to the region that they traverse. Those which pass over forests 
break the trees or even twist them in various directions. Others which 
traverse large prairies, suCh as the pampas of Buenos Ayres, the steppes 
of Turkestan, and the grassy countries of Central Africa, raise myriads of 
locusts in their tourbillons, and carry them either to other parts of the 
continent, where these insects instantly devour all the crops, or toward 
the ocean, where they are swallowed up. Sometimes the navigators en- 
counter, at considerable distances from the coast of Africa, real clouds of 
them that the tempests have raised from the ground and then consigned 
to the north-east trade-winds.f 

In the deserts of the Sahara, Arabia, Khorassan, India, and South Amer- 
ica, the winds raise enormous quantities of dust, and cause them to re- 
volve in space. At Buenos Ayres, the whirlwinds of 1805, and March, 
1866, were powerful enough to render the atmosphere as black as night, 
and to stifle pedestrians in the streets ; after the passage of the storm, the 
rain which fell showered mud upon the ground. Sometimes the masses 
of dust are columns revolving and dancing in immense circles like the 
genii of the air; sometimes, too, they are enormous cupolas whirling in 
space, covering hundreds and even thousands of yards in breadth, and de- 
veloping their ellipses for days together and to great distances. These 
whirlwinds render the atmosphere completely dark and irrespirable. In 
order not to be stifled, travelers are obliged to shut themselves up in all 
haste in their tents, and to throw themselves down Avith their faces to the 
earth, so as to form a rampart of their own bodies against the storm of 
sand. At the same time, the friction of all these grains of dust revolv- 
ing round one another disengages in a continuous manner real torrents 
of electricity. Above the whirlwind large birds of prey wheel in circles, 
either because they wish to enjoy the atmospheric equilibrium re-estab- 

* Eugfene Noel, Documents Inedits; Dagnin, Traite de Physique. 
t Lartigue, Systeme des Vents,, pp. 70, 71. 
18 



274 



THE ATMOSPHERE AND METEOROLOGY. 



lished by the storm, or because various small animals which are their food 
are carried along in the tourbillon.* 

In mountainous countries the whirlwinds can raise neither clouds of an- 
imalculse nor masses of dust, but they carry into space those heaps of 
snow so terrible for travelers ; more still, they remove even the pebbles 





Figs. 122, 123.— Whirlwinds of Dust. 

and fragments of schist, gneiss, and granite, making them whirl in circles 
which move rapidly with the conflicting aerial currents. The geologist 
Theobald has seen some of these whirlwinds of stones, which were no less 
than from fifteen to twenty yards wide ; it is not impossible, therefore, 
* De Khanikoff, Voyage dans le Khorassan ; Baddeley, Alexander Buchan, Meteorology. 



WATEE-SPOUTS AT SEA. 21b 

that certain masses of slaty fragments, which resemble piles raised by the 
hand of man, have been heaped up by whirlwinds.* 

The marine whirlwinds being phenomena of the same nature as the ter- 
restrial whirlwinds, must likewise raise particles from the surface that 
they traverse. The foam of the waves is sucked up by the aerial eddy, 
and ascends with a whirling movement. Sometimes the water swells, and 
rises in«great bubbles in the vacuum formed in the midst of the whirl- 
wind by the attraction of the air toward its circumference. In spite of 
popular accounts, it is very rarely that the water is carried up to the low 
clouds which brood over the sea so as to fall in a deluge at a great dis- 
tance : but the showers of salt-water which are discharojed far inland dur- 

• ... 

ing hurricanes prove that this phenomenon is not impossible, and that en- 
tire masses of fluid, not merely vapors or scattered drops, can be drawn 
up into the kind of chimney which the storm makes. It is said that ships 
threatened by a water-spout have succeeded in destroying with cannon 
this moving column of vapors, and In re-establishing the equilibrium of 
the atmosphere ; but when the water-spout is of considerable dimensions, 
the passage of a bullet through the whirling vapors can only have but 
very passing results. Besides, a water-spout is rarely an isolated phe- 
nomenon ; almost always it is connected with a tempest that the vessel 
can not escape. Generally, too, the influence of the aerial eddies makes 
itself felt to a great distance from their apparent limits. Thus the masts 
of a ship have been broken by the wind when on the deck no violent 
movement of the atmosphere was perceived, and the tempest still seemed 
to be distant. 

Unfortunately, it must be said that the whirlwinds are, of all meteoric 
phenomena, those which are least carefully studied. Nevertheless, it is 
certain that a profound knowledge of the various phenomena which oc- 
cur in the formation of these slight aerial eddies would enable us better 
to understand the grander cyclones, the entire system of the winds, and 
pei-haps even the movements of the heavenly bodies, and the rotation of 
nebulfe. In the same way as embryology has contributed, more than any 
other study, to the development of anthropological science, so it is by fol- 
lowing from the origin of its movement the particle of air which whirls 
in space that we shall be able to explain in a clearer and more precise 
manner the great facts relative to the circulation of the air or even to 
that of the celestial bodies. While the astronomer burns to comprehend 
some prodigious cycle of the stai's, too vast for his eye or his intellect, per- 
haps there exists under his eyes a simple whirl of leaves or dust, which 
he disdains even to look at, containing in its spirals the solution of the 
grand problem. 

* Theobald, Jahrbuch des Schweizer Alpen-Club, p. 534. 



' 
276 ' THE ATMOSPEEBE AND METEOUOLOGY. 



BOOK III.— CLOUDS AND EAINS. 



CHAPTER XIII. 

THE VAPOR OF WATER. THE MOISTURE OF THE AIR. ABSOLUTE MOISTURE 

AND RELATIVE MOISTURE. 

The air which moves and is mingled incessantly at the surface of the 
earth in breezes or in tempests, in whirlwinds or in cyclones, is at the 
same time the great agent for distributing the vapor of water. Owing 
to the movement of exchange which is established from one pole to the 
other between all the regions of the atmosphere, the water which evapo- 
rates from oceans, rivers, and inland lakes, distributes itself over all the 
countries of the globe, and even over the deserts. While the liquid sea 
washes only parts of the land,*a second sea borne by the atmosphere floats 
often invisibly over the circumference of the planet. 

Above every sheet of water, and even above ice, vapor is always formed, 
provided that the air be not already satui-ated ; that is to say, that it does 
not contain exactly the quantity with which it may be mixed without 
there being a precipitation of moisture. This limit of saturation varies 
with the temperature. At four degrees Fahrenheit below zero, a cubic 
yard of air can hardly contain more than fifteen grains Troy of vapor; at 
the temperature of melting ice it can not receive more than seven grains 
of moisture ; from fifty to eighty-six degrees Fahrenheit the number of 
grains that it ^absorbs corresponds nearly to the divisions of the ther- 
mometric scale ; but above eighty degrees the capacity of air for the vapor 
of water increases in a much more rapid manner. At two hundred and 
twelve degrees Fahrenheit the atmosphere can absorb its own. bulk, the 
tension of water becomes equal to that of air, and the phenomenon of 
ebullition is produced — that is to say, the vapor in formation counterbal- 
ances all the atmospheric column situated above. 

The vapor increases in the atmosphere in proportion to the increase of 
temperature ; such is the true meaning of the vulgar adage which attrib- 
utes to the sun the power of "pumping up the waters of the sea" to form 
clouds. Still, the same increase of atmospheric heat over two sheets of 
water of equal temperature does not necessarily produce the same quanti- 
ty of vapor ; the agitation of the air is also one of the most important ele- 
ments in assisting evaporation. In short, let the atmosphere be perfectly 
tranquil, and the portion which reposes above the waters will be soon 
saturated with moisture, and will not be able to absorb any more ; but 
let the aerial bed already charged with vapor be carried away by the 



THE MOISTURE OF THE AIM. 277 

wind, and replaced by a new stratum of dry air, this will likewise take its 
share of humidity, then those which follow will be saturated in their turn, 
and the phenomenon of evaporation will advance the more rapidly, the 
more violent the current of air itself is. We know with what speed the 
dry winds harden the fields and wet roads ; one would say that they lick 
the ground, so rapidly do all the pools of water disappear. 

After having thus facilitated evaporation on the sheets of water and 
moist parts of the continents, the winds transport vapor into the various 
countries of the earth, and mingle it with dry air, so that nowhere, even 
at thousands of miles from the ocean, is the air completely destitute of 
moisture. However, we easily understand that the quantity of vapor is 
not at equal temperatures distributed in a uniform manner. In open sea 
the atmosphere is always very near the point of saturation, even when the 
clouds do not threaten to discharge rain ; and consequently the vapor con- 
tained in the sea atmosphere diminishes pretty regularly from the equator 
toward the pgles, following the isothermal curves.* On the shores bathed 
by the moist air of the oceans, the proportion of watery vapor diminishes 
likewise in a normal manner on both sides of the equator. But in the in- 
terior of the continents, where the distribution of lakes, rivers, and mount- 
ains presents such a great variety, and where the winds follow such dif- 
ferent paths, the atmospheric vapor is also distributed very unequally. 
While the air is almost always either saturated with vapor, or very near 
the point of saturation, above England and Ireland, in the steppes of Cen- 
tral Asia it is of an extreme dryness, and usually it contains only from 
fifteen to twenty per cent, of the vapor which it could absorb. On an av- 
erage, the atmosphere of the continents contains three-fifths of the moist- 
ure which it would hold if it were completely saturated in all its extent. f 
This proportion is that which the surface of oceans or basins of evapora- 
tion, compared to that of the dry land, would have led us to suppose be- 
forehand. 

When the atmosphei'e contains all the moisture which its temperature 
can bear, the least particle of supplementary vapor is sufficient to deter- 
mine the precipitation under the form of drops of a part of the vaporized 
water ; either a mist or cloud is produced, and it begins to rain. Inas- 
much as the point of saturation varies in every country and at every sea- 
son, according to the oscillations of heat and cold, it follows that the same 
quantity of water contained in the atmosphere does not determine the 
ibrmation of rain at two different temperatures. The same proportion of 
moisture which, during the winter, completely saturates the cold air, and 
falls in snow to the ground again, would be very small in the heated at- 
mosphere of summer, and the aerial mass that should contain it would 
leave an impression of dryness ; in the same way a wind, such as the si- 
rocco, for example, would be dry in a warm country like Barbary, and be- 
come moist on the cold mountains of the Alps. J It is, therefore, impor- 

* See below, the section entitled Climates. 

t Saigey, Petite Physique du Globe. t See above, p. 243. 



2V8 



THE ATMOSPHERE AND METEOROLOGY. 



tant to distinguish clearly between absolute moisture and relative moist- 
ure. The first may increase gradually, while the second diminishes ; and 
though the air then would contain an increasingly greater proportion of 
atmospheric vapor, it would not the less appear little by little to become 
drier. 

This is, indeed, what takes place every day, as is proved by the long 
observations of the meteorologist Kamtz. In the morning, toward sun- 
rise, the temperature of the atmosphere is at its lowest ; and it is precisely 



£0' 






Ziirid>/ 
Fanlliom 



Mioriighl ^ e** a'^ Noon. i^ t^ ' S^ Midmgll 

Fig. 124.— Variations in the Hygrometi-ic Degrees at Ziirich and Faulhorn. 

then, or a little later, because of the vapors from the sun, that the air ap- 
proaches the point of saturation. In proportion as the heat and absolute 
moisture increase, the relative moisture diminishes, and then rises again 
when the sun sinks toward the horizon, and the temperature falls. Such 
is the contrast observed in a normal manner in the temperate countries 



20" 



15« 



mM§& 3^ 6^ 9** Hood. 3^ 6^ 9> Mdni^ 

Fig. 125.— Comparative states of the Thermometer and pygrometer at Halle in July. 

of Western Europe. When the opposite phenomenon presents itself, the 
cause is due to some great atmospheric disturbance, but the regular oscil- 
lations of moisture do not fail to re-establish themselves. The only re- 
gions where the air approaches the point of saturation in the warmest 
'hours of the day, are the high peaks toward which the vapors of the plain 
rise. Thus, while at Zurich, at the foot of the mountains, the relative 

































































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OSCILLATIONS OF ATMOSPHEIUC VAPOR. 279 

moisture is, on an average, much less in the afternoon than in the morn- 
ing, the exactly contrary phenomenon occurs on the Faulhorn, whose high 
■peak is often enveloped in clouds. 

During the various seasons of the year, the successive variations of 
which reproduce on a larger scale the progress of the day, the absolute 
moisture and relative moisture present the same contrast as at the cor- 
responding periods of the day ; in jjroportion as the heat increases and 
the quantity of watery vapor becomes greater, the air retreats from the 
point of saturation, and seems in consequence to become dryer and dry- 
er. This is shown by the preceding figure, borrowed from a work by 
Kamtz. Still, it is necessary to remember that these curves represent 
only averages, and that in reality the oscillations of the atmospheric va- 
por are much more complicated. In fact, every variation of temperature, 
every change of wind, modifies, either by slow gradations or by abrupt 
shocks, the condition of the air with respect to watery vapcn* ; dryness, 
moisture, and saturation succeed each other rapidly. Sometimes in a sin- 
gle day one can count a dozen showers and clearings up of the weather. 
The curves which should then represent the hygrometric state of the at- 
mosphere would be very complicated. 



280 THE ATMOSFHEBE AND METEOROLOGY. 



CHAPTER XIV. 

FORMATION OF MISTS AND CLOUDS. — HEIGHT, THICKNESS, FOEM, AND AS- 
PECT OF CLOUDS. 

When a mass of air resting on the ground becomes super-saturated 
with moisture, a certain portion of the vapor is immediately condensed in 
whitish drops, which, by their multitude, completely veil or hide all ob- 
jects, and only allow a dim light to pass through; these innumerable 
drops constitute mists. They are clouds still attached to the earth, and 
creeping along the plains or up the slopes of mountains. They are formed 
more especially in the night, because of the chilliness of the atmosphere ; 
often we see them rise in the evening from marshy surfaces and damp 
meadows. When a cold wind descends from the heights of the air, and 
retains moisture m its lower strata, the mist becomes permanent, and may 
last for days and even whole weeks. Frequently the sky is pure at a 
slight elevation above these vapors, and from the top of a summit which 
rises into free air we may then contemplate at our feet a great white sea, 
whence the hills spring up here and there like islands. 

The clouds, properly so called, are mists, which, instead of remaining at- 
tached to the ground, float suspended in the atmosphere at various heights 
above the earth. Whence comes it that the vapors imparted to the at- 
mosphere by the surface of the Avaters mount thus into space ? Such is 
the question which presents itself naturally to all inquiring minds, and 
which has formed the subject of many mythological fables. The discov- 
eries of modern natural philosophy have resolved this great problem in a 
general manner. It only remains now to elucidate certain secondary points. 

In consequence of the gradual decrease of temperature which the super- 
posed aerial strata generally experience on leaving the surface of the 
ground, the weight of the vapor in the atmosphere is much less in the 
higher regions than below. It results from this, that the expansive power 
of the moisture contained in the lower stratum of air is not balanced by 
the pressure of all the particles lying above it. The vapor from below 
rises, therefore, to the upper spaces, as a cork to the surface of the sea, till 
it has at last penetrated into a colder region of air, where it finds itself at 
its point of saturation, and is condensed in drops.* Every cloud that we 
see in the sky is therefore, according to Tyndall's expression, only the vis- 
ible summit of an ascending col«mn of vapor rising into the transparent 
atmosphere. 

The condensed particles of vapor are at first extremely fine ; but the 
air is never in repose, and the drops carried to the right or left by partial 
currents meet and unite in larger globules. On an average, as the meas- 
ures taken by Kamtz confirm, the diameter of the first nquid particles is 

* Saigey, Petite Physique du Globe. 



FOliMATION OF MISTS AND CLOUDS. 281 

60 small that no less than from twenty-five to thirty are needed to make 
.04 of an inch of thickness. But hundreds and thousands of them driven 
one against the other unite in smaller or larger drops, and when the drops 
at last reach the ground they are not less than a "02 of an inch in size, or 
even more. While they are still as fine and even lighter than dust, they 
are the playthings of the aerial currents, which toss, them, take them up 
as they fall, and carry them far away. Clouds of vapor are carried through 
space as the heavier eddies of sand from the plains very often are. Then, 
when the drops, constantly growing larger by the union of the particles 
dashed against each other, have become too heavy to allow themselves to 
be carried along like dust, they fall obliquely to the ground. According 
to the temperature, the force of the winds, and thickness of the clouds, 
they are either fine rains, showers, or I'eal deluges. 

Even when the atmosphere seems to be perfectly calm and no wind is 
blowing, it often happens that the clouds do not the less remain at a great 
height, as if they were lighter than the surrounding air. This is because 
an alternate and continued play of condensation and evaporation is then 
occurring in the thickness of the clouds and invisible vapors. The drops of 
rain already formed really fall from the cloud, but in the lower strata not 
yet saturated they are vaporized again ; then, mounting a second time to- 
ward the colder cloud, they are again condensed there, and in consequence 
their movement of descent recommences. A perpetual coming and going 
of particles of vapor, visible during their fall, and invisible during their 
ascent, is thus established on the lower surface of the cloud, which itself 
changes in dimensions and form, according to the least variations of the 
temperature. If the heat increases, the cloud will be gradually decreased ; 
if the air become a little colder, the haze of drops will increase in vol- 
ume. There are few sights which exceed in beauty that which is present- 
ed by a fine calm summer's afternoon, with clouds alternately formed and 
dissolved in the azure of the sky. We fii'st see a simple flake of vapor 
similar to a white bird floating in space ; but this flake grows, spreads, 
and is surrounded by undecided streamers; it is now a cloud still semi- 
transparent, allowing us to see the blue of the air through its rifts ;'then 
it is a real cloud developing its folds over the arch of the heavens. But 
let us look a few instants afterward, and already the cloud is destroyed; 
perhaps it has divided into numerous fragments, which, becoming smaller 
and smaller, are torn, scattered, melt, and disappear; we think we see 
them still, but it is an illusion, for the sky has resumed its blue. At other 
times, on the contrary, the first cloud that we have seen rise does not re- 
main isolated ; new masses of vapor ai-e condensed around it, and the 
space is gradually filled with floating clouds, which approach one another, 
join, and agglomerate ; and soon the sky, which seemed entirely free from 
vapor, presents in every part a thick stratum of clouds formed on the 
spot by the chilling of the atmosphere, and the condensation of the parti- 
cles of moisture. 

The height at which the clouds are formed and sustained varies in ev- 
ery season and ^untry, according to the temperature and direction of 



282 '^SE ATMOSPHERE AND METEOROLOGY. 

the winds. There are some, especially among the clouds chased by tem- 
pests, which touch the tops of buildings or trees ; others float at many 
hundred yards of elevation ;' others, again, are level with the highest 
"points of mountains, and all the aeronauts who have passed the summits 
of the great peaks in their ascents have seen strata of cloud far above 
their heads. • M. Liais estimated the height of seven and a quarter miles 
for the most elevated mass of vapors, the dimensions of which he took as- 
tronomically. This is an altitude exceeding by nearly two miles that of 
the highest mountain of the earth, and undoubtedly many clouds mount 
much higher still in the upper strata of the atmosphere. As to the mean 
elevation of the zone where the vapors are condensed, it seems to vary in 
the countries of Western Europe between one and a quarter and two 
miles ; it would, therefore, exceed the Vosges and mountains of Auvergne, 
and would only be overtopped by the ridge of the Pyrenees and the peaks 
of the Alps. Besides, this zone is necessarily variable because of the 
changes of temperature : it is higher in summer, and lower in winter. 

As to the thickness of the strata of clouds, it is no less various than the 
height at which the vapors are condensed. There exist clouds of all ver- 
tical dimensions, from the thin, transparent veil which allows the light of 
the stars to pass through, to those enoi'mous masses, superposed in strata 
three miles in thickness, like those that Barral and Bixio traversed in 
1850. M. Peytier has found-, by forty-eight measurements taken in the 
Pyrenees, that the thickness of the cloudy strata was, on an average, from 
four hundred and ninety to five hundred and fifty yards. According to 
Piazzi Smyth, this thiokness is ordinarily three hundred and thirty yards 
round the Island of Teneriffe, where the meteorological phenomena gener- 
ally present great regularity. Besides, it frequently happens that several 
layers of clouds mount one above another in the heights of the sky, and 
the total thickness of the masses of condensed vapor over one point of the 
earth is thus much augmented. These superposed strata of clouds are 
often due to the aerial currents and counter-currents which blow in oppo- 
site directions at various heights. But often, too, when the air is perfect- 
ly^ calm, we see some of these cloudy layers divided vertically in the at- 
mosphere. This is because the lowest stratum, once formed, constitutes 
for the upper spaces a sort of sea, the moisture of which evaporates under 
the rays of the sun, like that of the ocean or lakes situated below. The 
moisture changed thus into invisible vapors condenses in the colder air at 
a certain height, and forms a second stratum of clouds, which in its turn 
originates a third and more elevated layer.* 

In consequence of the different causes which give rise to vapors, the 
clouds assume the most varied appearances over the land, the sea, and 
even the rivers. It is said that the red men, those sagacious observers of 
all the phenomena of nature, knew, while they yet ranged the central 
plains of North America, how to recognize from afar the course of the 
Mississippi by the form of the clouds stretching above the river in elon- 
gated strata. Still it is principally round the outline of the islands of the 
* Saigey, Petite Physique du Globe. 



FOBM AND ASPECT OF CLOUDS. 283 

ocean that \ve can best observe this difference between terrestrial and 
maritime clouds. At Teneriffe the contrast occurs in the most striking 
manner. In summer the great white sheet of clouds which the trade- 
winds carry along is developed uniformly* over all the oceanic |maces. 
But in calm weather this bed of clouds terminates at a certain distance 
from the opposite flanks of the Peak of Teyde, in a kind of escarpment 
from six hundred to nine hundred feet high. Within this circle formed 
by the oceanic clouds the land is surrounded by its own zone of steaming 
vapors ; these latter, much lower than the larger clouds of the sea, attach 
themselves to the slopes in long fringes, moved in a very different way 
from that of the exterior zone, and quite distinct by the color and form of 
their folds. Piazzi Smyth, who was able thoroughly to study the phe- 
nomena of these various strata for many months, compares the terrestrial 
clouds of Teneriffe to that of land-ice which is formed around the islands 
and polar continents, and which constitute a solid platform, while the ice- 
fields in the open sea are broken by the currents, and carried away in 
fragments. 



Counter Ctirrent 

Sootb Noxth 

Fig. 126.— Winds and Clouds at Teneriffe. 

Meteorologists have attempted to class the clouds in various categories, 
according to their exterior appearance, but this is a very difficult under- 
taking, because of the infinite variety of forms, and the extreme mobility 
of the vapors which float in the sky. However, they have generally adopt- 
ed Howard's classification, according to which the clouds are referred to 
three great types — the cirrus., the cumulus., and the stratus — whicli mingle 
variously with each other, and thus produce secondary combinations, bear- 
ing the names of cirro-cunmlus^ cirro-stratus, and cumulo-stratus. These 
are, however, for the most part conventional divisions, which every meteor- 
ologist can modify at his pleasure, and Fitzroy has added ten varieties to 
the types and sub-types of clouds indicated by Howard. 
~ The cirri are small white clouds, as fine as carded wool or plumes of 
feathers ; these are the cats-tails of sailors, and are always perceived at a 
great height in the sky. According to Kamtz, their mean altitude is not 
less than four miles above the highest mountains and most elevated spaces 
to which aeronauts have attained. These slend^ cloudy filaments are 
still found, most often arranged in parallel rows, in the same direction as 
the trade-winds or counter trade-winds, which indicates the regularity of 
the aerial currents in the heights of the atmosphere. The cirri are 
formed of icy particles, as natural philosophers have been able to ascer- 



284 THE ATMOSPHERE AND METEOROLOGY. 

tain by the lumiDOus phenomena of reflection and refraction which occur 
in them. When the cirrus sinks and the crystals of ice are melted, the 
cloud gradually undergoes a modification of appearance, and changes into 
the qii-ro-stratus or cirro-cum*ulus. In the first case, its light whirls are 
mixed and confused in a cottony and grayish mass, prognostic of approach- 
ing i-ain ; in the second the sky is filled with those little dappled clouds, 
which by contrast give to the blue of the air such a beautiful hue. Accord- 
ing to popular legends, these are flocks of sheep grazing in aerial spaces. 

The cumulus which seamen distinguish under the name of " cotton bale " 
is distinguished from the cirrus by its origin no less than by its aspect. 
Instead of having been brought from very distant regions by the wind, 
it has generally been formed on the spot by the condensation of ascend- 
ing columns of vapor. We see this sort of cloud piled on the edge of the 
horizon in enormous rolls, with clearly defined outlines ; one might some- 
times think them to be gigantic chains of mountains, whose rounded white 
summits stand out against the deep azure. Their base is almost always 
horizontal, and spreads widely in an immense layer, indicating the precise 
zone of space where the invisible vapors coming from below are condensed 
into mist. The heavy cumulus, charged with an enormous weight of moist- 
ure, never rises to the same height as the cirrus, and hardly exceeds two 
miles in elevation ; the highest which M. Liais measured was at two miles. 
It mingles variously either witt5 the cirrus or stratus — that is to say, with 
those bands of clouds disposed in the sky in long sweeps or parallel strata. 
This form is what the mists most frequently afi"ect on detaching them- 
selves from the ground ; but it must be said, also, that clouds in reality 
most distinct resemble " stratus " when they are seen in perspective on 
the distant horizon. As to the " nimbus " of which some meteorologists 
have wished to make a special type, it is simply a rain-cloud which is de- 
veloped in the sky and breaks into showers. 

By the marvelous diversity of their forms, clouds are one of the great 
beauties of the atmosphere. Among all the images, whether fearful or 
graceful, that the fancy of man can dream of, there is not one which is 
not to be found in the vapors of space. By their fugitive outlines clouds 
resemble flights of birds, eagles with outstretched wings, groups of ani- 
mals, reclining giants, and monsters like those of fable. Other clouds are 
chains of mountains with snowy summits ; others, again, represent im- 
mense cities with gilded cupolas. Poets see in these groups distant archi- 
pelagoes, where the happiness so much sought for, and which does not 
exist on this earth, is to be found. Superstitious people, often pursued 
by the terror of their own crimes, see in them bundles of weapons, war- 
horses, armies in battle array, and massacres. The li^ht playing in this 
fantastic world of images increases still more their astonishing variety; 
all imaginable shades shine over these floating bodies from snowy white- 
ness to fiery red; the sun colors them successively with all the graduated 
tints of dawn, daylight, and sunset; meadows and forests are reflected 
there in greenish tones, and the sea itself is reproduced vaguely, by a col- 
or of metallic brilliancy I'ecalling that of copper or steel. 



RAIN CAUSED BY WIND. 285 

CHAPTER XV. 

INFLUENCE OP THE WINDS ON THE FORMATION OF SNOW AND KAIN. — 
DISTRIBUTION OF RAIN OVER PLAINS AND MOUNTAINS. 

Every aerial stratum containing aqueous vapor to the very point of 
saturation ii:iust necessarily let fall to the ground a certain quantity of 
drops, which are the cloud itself. If the air were perfectly calm these 
precipitations of moisture would always occur in a slow and continuous 
mann'er; the earth, enveloped in a constant mist, would, however, never 
be watered by heavy rains. Nevertheless, in almost all the countries of 
the world clouds and showers follow fine weather, and fine weather suc- 
ceeds to rain, owing to the winds, which meet in space and mingle air and 
moisture variously together. They purify the atmosphere from the su- 
perabundance of its vapors, and determine the formation of those sudden 
rains, without which the circulation of the waters and the general move- 
ment of life would be much less rapid on the surface of the globe. In 
fact, when two aerial masses unequally heated come in contact with one 
another and mingle, the temperature of the warmest suddenly sinks ; its 
capacity for holding vapor diminishes in consequence, and the moisture 
which it contains must be precipitated in rain. It is true that on its side 
the coldest wind is warmed and saturated by a greater quantity of vapor. 
But there is no compensation in this, for the point of saturation in the 
aerial strata is not exactly proportioned to the temperatures. If the two 
masses mingling assume a mean temperature between the two extremes, 
on the other hand, the capacity for holding vapor falls relatively below 
this average. Hence the immediate efiect of precipitation which occurs 
ordinarily at the time of the conflict of the winds, and especially at the 
mingling of the counter trade-winds, loaded with moisture, and the cold 
winds coming from the pole. It is then that we see clouds amass them- 
selves so rapidly in the sky and fall suddenly in violent showers. A few 
hours, sometimes even a few minutes, are sufticient for the blue of the air 
where the two winds meet, to be hidden by the dark folds of storm-clouds. 

At the Paris Observatory, it has been ascertained that the quantity of 
rain falling on the terrace of the building at ninety-one feet high is always 
less than the quantity of water collected in the courts situated below. 
This is because, in traversing the atmospheric strata saturated with moist- 
ure, each drop enlarges itself on the way by other scattered droplets, 
and continually brings back to the earth the pluvial moisture Avhich has 
evaporated. Perhaps, too, Ave ought to see in this increase of precipita- 
tion only a local fact, and attribute it in great part to an eddy of the 
drops in a kind of funnel formed by the court-yards of the building. At 
Paris the diiference between the respective quantities of rain which fall 



286 THE A TMOSPEEEE AND METEOR OLOOY. 

on Che terrace and into the court is about 2*4 ij^hes; at the summit of 
the edifice the annual depth of rain is 19'7 inches, while at the base this 
depth rises on an average to twenty-two inches. At Berlin the respective 
quantities of pluvial rain which fall on the roof and in the court-yard of 
the observatory are a little less, but the difference is also about a ninth. 

Still, we must not conclude from these facts that rains are less abun- 
dant on the mountains than in the countries lying at their foot. On the 
contrary, as the densest clouds always float at a considerable height above 
the low plains, it results from this that the most abundant rains fall on 
the slopes of the mountains. Driven by the wind, the moist masses strike 
against the cold rocks standing up across their route, and turn to rain ; 
the ravines and gorges are filled, while the lightened clouds mount the 
sides and cross the chain of mountains by the passes opening between 
the summits. This is a phenomenon which we can easily observe from 
the height of an advanced promontory, when the rain-clouds roll toward 
the mountains. Even when the lower plains do not receive a drop of rain, 
the sides of the mountains are inundated, and the torrents swell. Arriv- 
ing in blackish or copper-colored masses, which one would think were sol- 
id as rocks or metal, the clouds disappear in light grayish vapors; long 
after they have passed, a transparent mist may be seen hanging to the 
bushes and tree-tops. This is the superabundant rain which evaporates. 

Among the causes which determine a greater precipitation of moisture 
on the mountains than on the plains below, we must also reckon the dif- 
ference of temperature usually existing between the summits and the sur- 
rounding atmosphere. Durmg the day the slopes exposed to the warmth 
of the sun are more heated than the surrounding air, at least in calm 
weather ; but the ravines often remain much colder, and consequently the 
contact causes rain to fall by suddenly chilling the atmospheric strata. 
During the night, and at all times when the wind blows violently, the 
salient angles of the mountains become in their turn much colder than 
the sheltered gorges, and it is they that condense the mists of the air and 
cause the rain. How many times in mountainous countries, when the sky 
is perfectly clear and blue, do we not see the high j^eaks enveloped in a 
mist like the smoke of volcanoes ! These clouds, which we perceive 
around the summits, are found in warm air in the state of invisible va- 
pors ; it is the cold contact of the rocks or snows which has suddenly re- 
vealed them. The mountain peak thus announces to the inhabitants of 
the valleys that the atmosphere is saturated with vapors, and warns them 
of an approaching change in the temperature. The mountains thus con- 
stantly serve as meteorological indicators to the neighboring population, 
and In each mass of heights they always look toward one of the largest 
peaks, to see if it has "put on its cap" of clouds. 

Direct observations collected in various parts of the world have demon- 
strated that, all other things being equal, the annual precipitation of rain- 
water is in proportion to the altitude of the country, at least to a certain 
height in the mountains. According to Keith Johnston, the average rain- 



RAIX CAUSED BY 2I0UNTAINS. 



287 



fall for the plains would be 22-G inches per year in Europe, and for tlie 
mountainous districts about 51 inches ; this is about the pro[)ortion which 
is observed in Alsace. In the valley of the Rhine the quantity of rain is 
on an average from 22 to 22*8 inches in the year, Avhile on the high Vos- 
ges it is from 43 to 47 inches.* Alsace, therefore, is in this respect a re- 
sume of the entire continent. The Jura, arresting the passage of the winds 




Fig. 12T.— Raiu-fall ou the two sides of the Valley of the SaOne. 

which bear the vapor drawn from the ocean, forces them also to let fall 
their burden of moisture. By tracing a transverse line to the valley of 
the Saone from the heights of Charolais to the mountains of Jura, M. 
Fournet has ascertained that the annual precipitation increases tolerably 
regularly with the altitude; from 27*4 inches on the right bank of the 
Sa6ne it increases gradually to the parallel wall of the Jura ; on the west- 



Mo 





-s 








^ 




AH 

u 

§ 

00 


^t. 


■t ^" 




^^ 


gt-g 


t, 


*2 


tj0D<^ 


s 


t; 



Altitudes from West to East cm a level ■with Bour^ 

4) e o 






=0 SS " 



g teg p^ 



Sea- level 



Fig. 128.— Altitudes along the sides of the Valley of the Saone. 



ern side it becomes greater with the altitude, and thus from the height of 
the ground we could estimate the mean quantity of rain. 

On the southern slope of the Cevennes, where the winds blow with such 
violence because of the rapid variations of temperature produced by inso- 
lation and radiation, the difference which is observed between the annual 
falls of rain is still more considerable than at the foot of the other mount- 
ains of France. Over the town of Aries the total precipitation is 17-7 
inches ; but at some sixty miles to the north the town of Joyeuse, situated 
in the valley of Ardeclie, which overlooks the mountain rampart of" Ta- 
* Ch. Grad, Hydrologie de I'lll. 



288 THE ATIIOSPHEBE AND^ METEOROLOGY. 

riargue, received in 1811 as much as B^'G inches, and the annual mean is 
about 51 inches. On the 9th of October, 1827, enormous quantities (28*7 
inches) of water fell there in the space of twenty-one hours — more than 
falls, on an average, on the soil of France during a whole year. Hence the 
formidable inundations of the Ardeche.* To the east, in the valley of 
the Rhone, which the winds of the Mediterranean are able freely to as- 
cend, the annual fall of rain is always much less. 

On that side of the Alps turned toward the plains of Italy analogous 
phenomena are obseiwed. The mountains which close the Adriatic Gulf 
on the north receive twice, and in certain valleys even three times as 
much rain as the plains of Padua and the lagoons of Venice. But in Eu- 
rope it is principally on the shores of the ocean, where the west and south- 
west winds bring such a large quantity of vapor, that the action of mount- 
ains, or even of simple chains of hills, on the precipitation of moisture, is 
manifested in all its geological importance. At Lisbon the annual fall of 
rain-water is hardly 27 "6 inches, while at Coimbra, in a valley indenting 
the interior, there falls on an average 136 inches of water more than in 
most tropical countries. In the same way the little mountains of West- 
moreland, placed crossways to the kind of funnel which the Irish Channel 
forms, receive as much as 150 inches. In exceptional years this enormous 
quantity of rain-water is much exceeded ; and yet Liverpool, situated like- 
wise on the coast of the Irish Sea, receives in the same space of time 34 
inches of rain — that is to say, only one-fourth or one-fifth. As to the 
western coasts of Norway, which rise abruptly out of the sea, they are not 
exposed to less abundant rains than the hills of Burrowdale and Kendal, 
in Great Britain. At Bergen the annual fall of rain is 105 inches, and un- 
doubtedly other localities, whose fjords constitute real funnels where the 
wind from the open sea plunges laden with vapors from the Gulf Stream, 
are watered by a still more considerable quantity of rain. 

The countries of the world where the rain falls in the greatest abun- 
dance are probably the coasts of Malabar, those of Aracan, and the lower 
slopes of the Himalayas. There every thing favors the quantity of water 
to be very abundant in the rainy season : tropical heat, an enormous ba- 
sin of evaporation, and the height and direction of the mountain ramparts, 
which must retain the clouds, all assist to this end. Tlae Indian Ocean, 
an immense cavity in which the waters are incessantly revolving, and the 
superficial evaporation of which is more active than that of all the ether 
seas in the world, continually supplies the rain-clouds that the monsoon 
can-ies now toward the coasts of Africa, now toward those of Asia. There 
the mountains, placed directly aci-oss the aerial current, force it to rise 
over their slopes, and thus to mix with the colder atmospheric strata. A 
real deluge results from this : black clouds charged with rain let fall their 
enormous burden, the valleys are inundated, and the torrents changed 
into rivers. 

At Mahalabulechvar, situated at 4461 feet high on the western slope of 
* See The Earthy the section entitled Rivers. 



BAIN-FALL ON MOUNTAINS. 289 

« 

the Ghauts, the annual average of rain ascertained during a period of 
forty years is 2V5 inches. At Pondicherry, at the same altitude, on the 
Garrow Mountains, to the south of the valley of the Brahmapootra, the 
quantity of rain discharged annually by the clouds is much gi'eater — it is 
550 inches ; that is to say, it rains almost as much during the twelve 
months as at Alexandria during a century: in the single month of July, 
1857, as much as 148 inches fell there. It is probable that these enor- 
mous rain-falls have been even exceeded in several valleys of the Hima- 
layas, for Thomson and Hooker speak of a locality where the rain is not 







Cherralbigee Maiabukdwar Veta Cruz Bei^ Nantes Fans fixxseD&rw.(Eg}fptJ 

Fig. 129.— Comparative Amounts of Rain-fall. 

less than 470 inches in seven months, and where a temporary deluge of 
four hours, similar to the breaking of a water-spout, covered the ground 
with a liquid sheet estimated at thirty inches deep. In a single shower, 
therefore, this valley of the Indus had received proportionately as much 
water as France receives during a whole year. According to Cleghorn, 
the average of rain on the coast-lands of India was only 42*5 inches — scarce- 
ly the eighth part of that which falls on the mountains of the interior. It 
is from the enormous precipitation of moisture from the clouds brought 
by the monsoons that the base of the first counter-forts of the Himalayas 
are bordered with the unhealthy zone of the " Terai," whose jungles trav- 
elers are obliged to pass rapidly, so as to escape, by dint of speed, from 
fever and death. 

Nowhere, certainly, in other regions of the torrid zone is the precipita- 
tion of rain favored in so remarkable a manner. On the slopes of the 
Kiliman'djaro it rains almost every day during ten months ; but the trav- 
eler Von der Decken, who was the first to ascertain this meteorological 
fact, does not say that the rains fall as abundantly as in India. In the 
Gulf of Guinea the monsoons, which are precipitated toward the conti- 
nent, meeting with but few mountains that present an obstacle, carry 
their rains far into the interior of Africa. The Antilles have not enough 
breadth to hinder the winds and clouds from deviating ^liquely to right 
and left, and the greatest annual quantities of rain that have been ascer- 
tained there in the high mountain gorges do not attain 390 inches, which 
is 195 inches less than at Pondicherry. On the coasts of Colombia, the 
chain of the Andes, relatively but little elevated, and here and there in- 

19 



290 THE ATMOSPHERE AND METEOROLOGY. 

terrupted by wide valleys, presents itself obliquely to the direction of the 
trade-winds ; but in the funnel of the Gulf of Uraba, and in the almost 
impenetrable forests of the province of Choco, the rain falls in truly pro- 
digious quantities, hardly inferior to those of the Himalayas. It is to this 
enormous precipitation of moisture that the Ata'ato, a river relatively in- 
significant by the length' of its course, rolls along a quantity of water 
greater on an average than that of the largest rivers in Europe.* 

Whatever may be the diiference between the rains in various climates, 
this phenomenon of a greater abundance of rain on the slopes of the mount- 
ains than in the plains is a general fact over all the earth. We observe 
it in India as in Europe, in Patagonia as in the Antilles. Still, we must 
not conclude from this that the precipitation of moisture increases in an 
indefinite manner in proportion to the height of the mountains, and that 
the summits always receive the greatest quantity of water under the form 
of snow or rain. On the contrary, it is certain that above the zone where 
the thickest clouds generally float the rain diminishes by degrees. The 
want of precise observations prevents us from indicating the average 
height of this zone in the various countries of the world, and, consequent- 
ly, we can not yet determine the laws of distribution of rain in a vertical 
direction. But methodical researches on the movements of the clouds 
will, little by little, furnish all the elements necessary, and will allow us, 
sooner or later, to point out on each mountain slope the spot where the 
greatest quantity of vapor will every year be transformed into water. 

In the Alps of Switzerland this zone of the greatest precipitation is tol- 
erably high, for the total bulk of snow-water and rain which falls annual- 
ly at the pass of Great St. Bernard exceeds by more than 39 inches that 
which is collected at Geneva, at the foot of the mountains. Below it is 
only 32"5 inches, while on the snowy pass it is, on an average, 79 inches. 
Figures are wanting to establish the fact that on other mountain chains 
the elevated slopes receive a much less quantity of water than what falls 
in the valleys opening half-way up. But this is a phenomenon not the 
less* certain, owing to the researches already made on the mean height of 
the clouds. As to the mountain slopes which are not struck by the rainy 
winds, and the plateaux surrounded by terraces, they only receive in gen- 
eral a very slight proportion of rain, and a number of them are, owing to 
want of water, transformed into real deserts.f The peaks which rise 
above the atmospheric currents arrest the clouds en route, and only allow 
dry winds to pass. Thus the plateaux of Castile are only traversed by 
meagre rivulets, while through every valley of the Cantabrian Pyrenees 
there flows a pretty considerable river. It is the same in Colombia ; on 
the abrupt coasts which the trade-winds strike against, the mean depth 
of rain-water is^ptimated at 81 inches per year, and on the plateaux of the 
interior it appears to be only 41 inches. At Bogota, in the centre of the 
plateau of Cundinamarca, it is 43"5 inches — hardly as much as on the high 

* See The Earth, the section entitled Rivers. 
t See below, p. 301 . 



RAIN-FALLS ON MOUNTAINS. • 291 

Vosges, in the temperate climate of Europe.* Finally, the rain which 
falls on the high plains of the Deccan, on the eastern slope of the Ghauts, 
would be considered insufficient in most countries of Europe, where, how- 
ever, the evaporation is much less than in Hindoostan. At Poonah, situ- 
ated on the plateau immediately to the east of the mountains which over- 
look Bombay, the annual fall of rain is only 23"5 inches. 
* Agostino Codazzi, Caldas, Illingworth. 



292 ^'■SS ATMOSPHERE AND METEOMOLOOY. 



CHAPTER XVI. 

TROPICAL EAINS. — EAINT AND DRY SEASONS. — PERIODICITY OP RAINS. 

The form and relief of lands, as well as the situation which they occu- 
py relatively to the extent of ocean, are not the only facts that influence 
the greater or smaller precipitation of rain in various countries ; we must 
also take temperature into account. All other things being equal, it rains 
more in a country the nearer it is to the equator ; for the evaporation in- 
creases with the heat of the sun, and consequently the condensation of 
moisture produced by the conflict of the winds returns a greater quanti- 
ty of water to the earth. Hotter than the temperate zones, the tropical 
zone is also watered by more abundant rains, in the same way as the tem- 
perate zones receive proportionately more moisture in the shape of rain 
and snow than the two polar zones. 

Between the tropics the rains follow with tolerable regularity the ap- 
parent course of the sun, and the season during which they fall to the 
ground is thus clearly defined. In fact, the trade-winds become charged 
with an enormous quantity of watery vapor in passing over the seas of 
the torrid zone ; but their temperature augmenting in proportion as they 
approach the equator, they acquire a greater and greater capability of 
holding moisture, and preserve their relative dryness. Nevertheless, as 
soon as the regular winds from the south-east and north-east have ar- 
rived at their point of meeting in the equatorial zone, things suddenly 
change; the two aerial currents mount together into the high regions of 
the atmosphere, their temperature is lowered, the vapor with which they 
are saturated condenses, heavy strata of clouds are formed above the 
whole of the zone of calms, and are precipitated in floods of rain. The 
water falls, indeed, in such great abundance that sailors are often able to 
collect from the surface of the ocean the fresh-water*hat they need. The 
English navigators have given to these parts of the sea the expressive 
name of sioamp, as if the sea were changed into a sheet of brackish wa- 
ter ; for Frenchmen the entire region has become the Pot-au-Noir — prob- 
ably because of those sudden showers and irregular winds which succeed 
to the downfall of the rain. The zone of clouds which extends tnus in a 
more or less continuous manner all over the ocean is undoubtedly visible 
from the nearest heavenly bodies, and must resemble those whitish bands 
which our telescopes discover on the planet Jupiter. 

The movement of the zone of clouds with the course of the sun over the 
ecliptic causes the dry and rainy seasons to alternate regularly in the trop- 
ical regions. Thus the Antilles and the republics of the American isthmus 
are successively under the great girdle of rainy clouds, and in the domain 
of dry winds. During the months of June, July, and August, the sun, 



RAINY AND DRY SEASONS. 



293 



trailing beneath him the immense veil of vapors, is at the zenith of the 
countries near the Tropic of Cancer ; this is then the so-called winter-sea- 
son, or hwernage; vapors cover the heavens, and rain falls in abundance. 
As we may see, by a comparison of the rain at Vera Cruz and on the 
northern coasts of the Gulf of Mexico, the quantity of rain that falls ex- 
ceeds by double or triple the average proportion of water received by 
the border countries situated beyond the zone of " hivernage." In Sep- 
tember, when the girdle of clouds has again passed southward, the trade- 
winds res«me their normal march in the direction of the equator. They 
absorb the moisture of the land and sea, and carry it farther to the coun- 
tries sheltered by the zone of clouds ; then it is the dry season for the 
Antilles and Central America. 

Depths 
200™^. 



ieo"?3_ 



gQinsj 



6.0> 



IttB^nS 




VefaCruz S^AntonioN^Orleans Natchez VLcksburg Memohis Mobile Cedflr-keys Sl-Augustine 
Fig. 130.— Rains around the Gulf of Mexico. 

In Colombia the year is divided into four periods, two dry seasons and 
two wet seasons, produced likewise by the oscillation of the rainy zone. 
During the winter of the northern hemisphere the girdle of calms pene- 
trates into the opposite hemisphere, and extends in breadth from the sec- 
ond degree of north latitude to the fifth degree of south latitude. When 
New Granada is still under the influence of the trade-winds from the north- 
east the sky is pure and cloudless ; this is the spring season, the verano ; 
i^ rains only in the mountain valleys which cross the path of the winds. 
Toward the months of May and June, the girdle of calms is brought back 
to the north, and passes above the plateaux of Granada, inundating them 
with rain; this is the first hivernage — the invierno. But the cloudy mass- 
es continue their»march toward the north, and stay only after having at- 
tained the twelfth or even the fifteenth degree of north latitude. Then 
the Colombian plateaux are outside the zone of precipitation for the sec- 
ond time, and subjected to the influence of winds greedy for moist«l-e, 
which bring with them a new dry season. Finally, toward the months 
of November and December the o;irdle of calms again crosses the latitude 



294 



THE ATMOSPHERE AND METEOROLOGY. 



of Bogota, and the thirsty land instantly receives rain from the sky, till 
the wide band of clouds has disappeared in the direction of the equator.* 
To the south of the countries where the two annual passages of the 
cloudy xone cause the alternation of a double winter and a double sum- 
mer, phenomena analogous to those of the Antilles and Guatemala occui\ 
In the regions of the Upper Amazons, as in Central America, there are 
only two seasons, the rainy and the dry, but these follow each other in in- 
verse order : when it rains on one side, the sky is azure on the other ; when 
drought prevails to the south, the lands are inundated to the north. Be- 
sides, in both hemispheres the normal epoch and the abuudance of the 
rains are variously modified by the form of the coasts, the relief of the 




Jaa. Fet. Mar. April May June Juljr Atig. Sept. Oct. Nov. Dec. Jan. 

Fig. 131.— Amount of monthly Rain-falls at Anjarakandy, Calcutta, and Madras. 

plateaux and mountains of the interior, and the alternations of the mon- 
soons. Thus the great rains fall in June and July at Calcutta, and at 
Anjarakandy, on the coast of Malabar; at Madras th^ maximum is in 
November. 

By a remarkable contrast, it is precisely at the time of the year when 
thg heat ought to be greatest that the tropical countries are most re- 
freshed by the precipitation of abundant rains. Extending like an im- 
* Maury, Geography of the Sea. 



TROPICAL RAINS. 



295 



mense veil, the clouds protect the earth from the heat of the sun, which 
is then at its highest in the heavens. The winter-time, during which the 
temperature is often lower than in the warm season, is nevertheless the 
true summer, from an astronomical point of view. We can judge of the 
influence which the tropical rains exercise on the temperature by the ac- 
companying figure, the two' lines on which represent — one the monthly 
amount of pluvial water at Anjarakandy, and the other the thermomet- 
rical variations. Thus the oscillation of the zone of clouds results in 
equalizing the annual heat, and tempers the ardor of a summer which 
might be in the whole of the tropical zone what it is in the Sahara. It 
is true that often one feels more oppressed in the rainy season than in that 
of the great heat, because of the enervating moisture of the atmosphere. 



Depths ofwatei' 




:i? • 



Jan. RbMar. Apr. Maj- June July Aug Sept Oct Nov Dec. Jan. 
Fig. 132.— Amounts of Rain-fall at Anjarakandy, with the corresponding Temperatures. 

Besides, we must not think that during the tropical rains moisture is 
precipitated constantly, or even frequently, at all hours of day and night. 
On the contrary, in the greater part of the equatoriaj regions the rains 
obey a sort of rhythm. Ordinarily, they only commence in the afternoon, 
because during the night and morning the atmosphere has not yet had 
time to be completely saturated with vapors; but when the air can no 
longer absorb any more moisture, the storm breaks violently in the midst 



296 THE ATMOSPHEBE AND METEOROLOGY. 

of rapidly condensing clouds. On many points of the coast-line of the sea 
of the Antilles, in Colombia and Mexico, the sky begins to discharge its 
burden of rain toward two o'clock in the afternoon; but the shower is ex- 
pected, and all preparations for shelter are made beforehand, and in the 
evening one may go out-of-doors again without fear. In the same way 
in certain parts of tropical Brazil, the hours of the daily storm are so well 
foreseen that rendezvous can be appointed at the end of the rain. How- 
ever, there are tropical countries more abundantly watered where the 
showers of each day last till a late hour at night, or even into the morn- 
ing. On the open sea, where the immense surface of evaporation can con- 
tinually saturate the superincumbent atmosphere, the rains have a longer 
duration than on land, and they often continue for whole days. 



EAINS BEYOND THE TROPICS. 297 



CHAPTER XVII. 

KAINS BEYOND THE TROPICS. — WINTER RAINS. — RAINS OP SPRING AND 
AUTUMN. SUMMER RAINS. RAINS OF THE POLAR REGIONS. 

To the north and south of the zone of the trade-winds, the rains, like 
the winds, present much less regularity than in the region of the equato- 
rial calms, both in the quantity of rain that falls and in the time, and dura- 
tion of the rainy season. It is in the northern hemisphere especially that 
the precipitation of rain is accomplished in an unequal manner, for the 
surface is there more varied than anywhere else by the contours of con- 
tinents, scattered islands, inland seas, and chains of mountains, which lie 
parallel, oblique, or transverse to the winds. Thus it is very difficult in 
many countries to discover the general order in w^hich the rains succeed 
each other ; and so long as conscientious observations have not been made 
during any series of years, uncertainty must prevail in this respect. 

However, the registers kept at the various meteorological stations of 
the northern hemisphere are already sufficient to show what is the normal 
distribu'tion of the rains on this side of the Tropic of Cancer. To the 
north of the variable limit where the trade-winds commence, and as high 
as a latitude of forty degrees, the rains fall almost exclusively during the 
winter. Around the basin of the Tyrrhenian Sea, and on the coasts of 
Western Europe, they are distributed throughout the year, but it is es- 
pecially in autumn that the greatest precipitation of moisture takes place ; 
more to the north it is the summer which is the especial rainy season ; 
finally, in polar countries it is in the winter that the condensation of the 
clouds iDi'oduces the most rain and snow. 

The direction of the winds is the true cause of this unequal distribution 
of the rain-fall according to the various parts of the year; for beyond the 
equatorial zone most of the showers are, so to speak, not formed on the 
spot by the condensation of the ascending vapors, but are brought from 
afar by the currents of the atmosphere. During the winter of the north- 
ern hemisphere the whole system of trade-winds is attracted to the south, 
following the sun, and consequently the aerial counter-currents which re; 
turn toward the Arctic pole can descend again to the surface of the globe 
in the neighborhood of the Tropic of Cancer.* The vapors with which 
these winds are charged are then condensed into rain in consequence of 
the mingling of the air which carries them with other and colder atmos- 
pheric masses ; this is the rainy season. But when the sun approaches 
the equator, bringing with it toward the north the entire system of winds, 
the counter trade-windi of the south-west can not then approach the sur- 
face except toward the middle of the temperate zone. The sky becomes 

* See above, p. 232. 



298 THE A TMOSPHEBE AND METEOBOL G Y. 

Ti^rtPt JEm^rcbTyMEiTGh Apiil May June July Au.g^ SepL*^^ Ociy Kov?- Dec? 



9B5f^ 



820ft 



essf.^ 



490 ft- 



32 5 f^ 



160 f^ 




Disciharie 
oftbem 



Fig. 133.— Amouut of Eain-fall in the Basin of the 111, and mean Discharge of the River during 

the Year 1856. 

bright again in the regions which had been inundated with rain ; a rela- 
tively dry period commences in the spring, and lasts until the sun has 
again crossed the equator toward the southern lands. This alternation of 
the seasons is accomplished with great regularity on the coasts of Califor- 
nia and Oregon, at Madeira, in Algeria, and on the coasts of Portugal. It 
is thus that at Lisbon only 0"16 inch of rain falls in July, while in Decem- 
her the total precipitation is 4*9 inches. At Naples, and even at Rome, 
summer droughts rarely disturbed by showers follow the winter rains. 

As to the region of the spring and autumn rains, it ought to comprise 
the countries over which the returning trade-winds blow at the epoch 
when the sun is at the zenith of the equator; this is the equinoctial period 
of March or September. In certain countries in the south of Europe, and 
especially in Provence, we observe, in fact, that the rains are most abun- 
dant in spring and autumn. Even in Alsace the greatest quantity of rain 
falls in spring, and flows into the tributaries of the Rhine, as shown in 
figure on opposite page, borrowed from a work of M. Charles Grad;* but, 
with some exceptions, the maximum of autumn is generally the highest of 
the two, and that of the spring ends by disappearing entirely in a north- 

* Hydrologie de fill. 



BAINS OF THJ^J POLAR REGIONS. 



299 















./y^ 


^A_ 


i-r-:::;^^ 


^"^\^>^ 


ii/'^ 


"^%^ 


"^"■■"A 




J 













"Winter Spring ^urnmer 
Fig. 134. 

A. Western France. — B. Basin of the Rhone 
to the South of yiviers. — C. Basin of the 
Rhone to the North of Viviers. Autumn 
Rains in France D. Eastern France. 



erly direction. The western coasts of France and the British Islands are 
comprised Avithin this zone, where the autumnal rains regularly predomi- 
incKes nate. The true cause of this excess of 

precipitation during the autumn season, 
compared with spring, has not yet been 
proved ; it must doubtless be sought in 
the fact that, under the influence of the 
various atmospheric and marine currents, 
the fall of the temperature after the heat 
A^t — ^^tec ^^' summer is accomplished in a relative- 
ly abrupt manner. The descent of the 
thermometer in autumn is more rapid 
than its ascent in spring. This is the re- 
sult we obtain from most of the meteor- 
ological tables kept in the countries of Europe and North America. 

More to the north, in the temperate zone, it is no longer in autumn but 
in summer that the rains water the earth with the greatest abundance. In 
the whole of Central Europe, from the Vosges to the Ural Mountains and 
beyond to the shores of the Sea of Okhotsk, the greatest precipitation of 
moisture takes place in the warmest part of the year. This is because the 
sun, being then above the Tropic of Can- -jacaues 
cer, has brought back to the north the en- 
tire system of the trade-winds and counter 
trade -winds; these latter, therefore, de- 
scend to the surface of the earth in high 
latitudes only, and there alone, in conse- 
quence of their conflict with the cold 
winds of the polar regions, is produced 
this notable increase of rain, owing to va- 
pors brought from the tropics. 

On the other side-^of the equator it is in exactly the opposite way that 
the counter trade-wmds of the north-west, traveling with the sun, deter- 
mine the greatest precipitation of moisture over the countries toward which 
they sink. ■ As to the snows of the two polar zones, they fall most of all in 
winter — that is to say, during the long night which lasts several months — 
for the temperature of the atmosphere is then too low to retain in sus- 
pension the moisture brought by the equatorial winds. 



iC 












f y^ 


">^ 


--r^ 


8 

4 


V^^^ 


*/ .••■ 


'^_,.-'^ V 


\ •••••• 


zizy 






^ 






» 





WinteK Spring STmrmer Ant. "WLntes 

Fig. 135.— Autumn and Summer Rains in 

the Temperate Regions of Europe. 



300 THE ATMOSPEEBE AND METEOROLOGY. 



CHAPTER XVIII. 

COUNTEIES WITHOUT EAIN-. — GEOLOGICAL ACTION OP EAINS. — CONTRAST OF 
THE TWO HEMISPHEEES. 

Thus in all parts of the earth, from the equator to the poles, the rain is 
distributed with a certain regularity, according to the seasons. In many 
regions it falls exclusively during a fixed period of the year ; in other 
countries the alternation is not divided so clearly between the rainy and 
the dry season. It often rains during the winter months as well as dur- 
ing the summer months. But a regular oscillation is observed between the 
two periods of the greatest and least precipitation. Still, there are cer- 
tain countries where rain is almost entirely wanting, and these countries 
are found, for the most part, situated precisely in the neighborhood of the 
equator and the tropics, where the waters, heated by the sun, furnish the 
greatest quantity of vapor to the atmosphere. In regions like the coast- 
line of Peru, which stretch at the foot of high mountain ridges rising on 
the path of the rainy winds, the constant dryness of the atmosphere must 
be solely attributed to the form of the surface of our planet. It is some- 
times sufficient to cross a single pass to ascertain the enormous difference 
which exists, in a meteorological point of view, between the two slopes. 
On one side, the winds, laden with moisture, frequently let fall their bur- 
deij of rain ; on the other side, the .aerial currents, lightened of their va- 
pors and' heated by the reverberation from the white rocks and bare 
earth, greedily absorb, on the contrary, the little water which flows in 
the valleys. The trade-winds from the north-east and south-east, which 
discharge on the eastern slopes of the Cordilleras such an abundance of 
rain as to form the Japura, the Putumayo, the Upp(ji' Maranon, the Apu- 
rimac, the Mamore, and so many other mighty tributaries of the magnifi- 
cent current of the Amazons, do not let a single drop fall on the western 
slope, which is transformed almost into a desert, and traverse the surface 
of the Pacific to a great distance into the open sea before having collected 
enough vapor to discharge fresh rains. On the coasts of Peru the air is 
often misty ; but through this whitish veil the blue sky can be always 
distinguished ; the appearance of a cloud is a real event, and the whole 
population assembles to contemplate this unaccustomed spectacle. On 
the western shores of Mexico, where the winds are much less regular than 
in South America, the atmospheric disturbances occasion the fall of vio- 
lent showers at times ; but, as in Peru, the great mass of rain-water is re- 
tained by the plateaux, and mountains which rise to the east, across the 
path of the trade-winds and monsoons. More to the north the meteoro- 
logical phenomena occur in an inverted order. The rainy winds which 
strike the summits of the coast range and Sierra Nevada are the counter 



RAINLESS COUNTRIES. 301 

trade-winds of the south-east ; they abundantly water the slope which 
faces the Pacific, Bq^ beyond the Rocky Mountains they are entirely 
dried up, and the deserts of Texas, New Mexico, and Colorado would be 
absolutely without water if the monsoons from the south did not bring 
some moisture. The mean quantity of rain which falls in the solitudes to 
the west of the Mississippi is estimated at two inches only.* 

But in the neighborhood of the tropics, and even some way into the 
temperate zone, there are other regions freely traversed by winds laden 
with vapors, which are nevertheless very rarely watered by rains. A 
wide tract of land almost without water stretches diagonally across the 
CMd World from the western plains of Africa to the plateau of Eastern 
China. This zone, disposed in an immense arc, the concavity of which is 
turned toward the north-west, comprehends a great part of the Sahara, 
the deserts of Egypt and Arabia, the high lands of Iran, various tracts of 
Tartary and China, and the plateau of Gobi. In the southern hemisphere, 
the three continents, Africa, Australia, and South America, have also each 
their zone of dry lands situated in the neighborhood of the Tropic of 
Capricorn. In Africa it is the Desert of Kalahari ; in Australia it is the 
fearful solitudes which explorers have to traverse on their way from the 
southern colonies to the Gulf of Carpentaria ; in South America it is the 
Pampas. If these several countries to the north and south of the equator 
are thus destitute of rain-water, the cause is principally the trade-winds, 
which, in their regular passage across the continents, constantly absorb 
fresh quantities of vapor in proportion as they approach the zone of the 
equatorial calms; and their temperature also increases. Nevertheless, it 
would be very difficult to trace the exact boundary of the regions desti- 
tute of rain with those where the precipitation takes place regularly, for 
all round the countries of prolong^ drought the monsoons form a sort 
of irregular border, changing year by year. Besides, the plateaux and 
groups of mountains placed in the midst of desert regions, the Djebel- 
Hoggar in the Sahara, the Demavend to the north of Persia, the huge 
pile of Cordova in the Argentine Pampas, raise their summits high into 
the air, and force the chilled winds to yield to them a part of the vapors 
that are carried toward the equatorial zone. As to the plateau of Gobi, 
situated in great part beyond the zone of the trade-winds, the dryness of 
its climate is caused by the ifiountains which surround it, and by its dis- 
tance from the sea. 

As is shown by the aspect of all deserts, rain is the great geological 
agent on the surface of the earth. The immense indentations made in 
the edges of plateaux and the flanks of mountains are due, for the most 
part, to the action of rains and streams which wear away the clays, carry 
the sands along with them, lay bare the rocks and drive them before them, 
and also assist in the destruction of the shores. In all the rainy countries 
whose surface is greatly varied, it is absolutely impossible to recognize 
what was the primitive aspect of the land, so much has been done by the 
* See The Earth, the section entitled Plains. 



302 



THE ATMOSPHERE AND METEOROLOGY. 




Fig. 136.— Ravines m the Craters of Ecnniou. 



rains in sculpturing anew the fissures and inequalities produced at first 
by other agents. Thus in most of the volcanic countries, and especially 
in the island of Reunion, the ancient craters have been hollowed out and 
worn by the rain, and finally transformed into circles similar to circles of 
erosion. According to Lyell, the Val del Bove, which opens on the east- 
ern slope of Etna, is also an ancient volcanic crater whose walls have been 
partially destroyed by the rains.* 

Where rain is wanting, the surface presents a singular monotony over 
vast tracts. It is undoubtedly to the absence of rain and the dryness of 
the atmosphere that the Argentine Andes owe the peculiar uniformity of 
their relief; there we see none of those long valleys, those deep ravines, 
and wide, crumbling circles, which give such a picturesque character to 
the architecture of the Pyrenees and the Alps. Since the epoch when 

* Philosophical Transactions, 1858. See, also, The Earth, the section entitled Volcanoes. 



The Ocean, <!icc 



RAIN Map 




Eng^Ly Erhard. 



HAilPER &. BRC 



The World. 



PL. xrv 




More than: ISvvches of rain 
I J from 39 inches of rain 
L_Ij froTTLStDSS inrhe.f of rain, 
I — ^ less than H uicJiAs- of rain, 
I I r/ii////;w retfions. 



S, NEW YORK. 



Vincent Bronk , i j j y /.' SaiL.Liiii, 



EROSIVE ACTION OF RAIK 3O3 

the waters of the sea retired, carrying to the foot of these mountains of 
the New World the enormous heaps of rolled pebbles which we see there 
now, the snows and rains have not yet fallen in sufficient abundance to 
hollow out? the declivities and cut them into valleys and counter-forts. 
From below, the rampart of mountains presents the aspect of a uniform 
and blackish wall, above which rise here and there a few peaks striped 
with white lines. The plateau, from 13,000 to 14,000 feet in average 
height, upon which these isolated mountains rise, is in many places almost 
perfectly Jevel over a breadth of fifty miles. A few low hills scarcely 
break, from time to time, the monotony of the great plain ; in the deepest 
depressions small lagoons of water, almost always very saline, are seen. 
The vegetation is absolutely nothing, not because of the intensity of the 
cold, but because of the dryness of the air and the violence of the wind 
which blows in these high regions ; one single plant grows at the height 
of 13,000 feet— rthe Llareta, a kind of lichen with a strong root, which 
spreads over the rocks like a green mold. The snow, which rarely falls 
on these heights, melts or evaporates when it has barely escaped from the 
clouds. In the middle of the day these snow vapors rise in thin clouds, 
which are lost at great heights in the Jalue atmosphere ; one would sav 
they were fire-works ascending into the sky.* The air of these regions is 
sometimes so dry that the skins of travelers crack, and their nails break 
like glass. f 

The exact proportion of rain which falls in the various countries of the 
earth, so indispensable to our knowledge of meteorological laws, is thus 
foilnd to be also of the greatest importance in a geological point of view; 
since it enables us to explain the form of the mountains, the general as- 
pect of countries, and the state of the vegetation which covers them. 
This k nt)t all ; the distribution of rain is likewise an astronomical phe- 
nomenon ; for by the comparison of the amounts of rain fall observed 
over the surface of the globe, one can learn exactly the contrast which is 
presented between the two hemispheres in respect of the precipitation of 
moisture. And this contrast, whatever its importance may be, is inti- 
mately connected with the unequal distribution of heat in the two halves 
of the planet, and in consequence of the form of the orbit*which the earth 
describes round the sun. 

It results, from a comparison of observations, that the greatest propor- 
tion of rain-water *falls in the northern hemisphere. According to Keith 
Johnston, who unfortunately was able to quote but a somewhat limited 
number of meteorological facts, the amount of rain which falls on an aver- 
age during the year on the surface of the earth to the south of the equa- 
tor is twenty-six inches ; to the north it is about thirty-seven inches and 
a half — that is to say, about half as much again. J 

These figures seem a little too high, and will undoubtedly be sensibly 

* Martin de Moussy, Confederation Argentine, vol. i., p. 187. 
t Tschudi, Ergdzungsheft Mittheilungen von Petermann. 1860. 
X Physical A tlas. 



304 THE ATMOSPHERE AND METEOROLOGY. 

modified by future researches, which embrace a greater number of sta- 
tions and a longer period of years. But it is very probable that the dif- 
ference noticed between the two hemispheres in respect of the precipita- 
tion of rain-water will always remain considerable. In fact,nt is in the 
northern hemisphere that we find the zone of equatorial calms where the 
rains fa,ll in the greatest abundance during almost all the year. It is in 
the northern hemisphere, too, that the monsoons attracted by the heated 
continents discharge those prodigious showers, and supply the earth in a 
few weeks with more water than falls from the clouds in othe^- climates 
in several years. Almost all the great rivers, alsOj with the exception of 
those which flow into the estuary of La Plata and the tributaries of the 
right bank of the Amazons, have their source in the northern hemisphere.* 
The continental surface which is found to the north of the equator is three 
times the extent of that which stretches to the south, while the amount 
of rain, estimated roughly according to the yet incomjDlete data which we 
possess, is at least five or six times as great. 

Now, by a remarkable contrast, the northern hemisphere, which re- 
ceives the greatest quantity of water, supplies the least proportion of it. 
In fact, the ocean, restricted to the north by continents, spreads on the 
south of the equator, so as to cover almost the entire circumference of the 
earth. It thus presents to the solar rays an immense surface of evapora- 
tion, incessantly feeding the clouds of the atmosphere. In this way that 
half of the globe which furnishes the most vapors is that which receives 
the least rain in exchange ; a circuit of the aerial currents is, therefore, 
necessarily established between the two hemispheres, and thus equilib- 
rium is maintained. It is in great part the vapors from the Southern At- 
lantic, and perhaps also from the South Sea, that supply the rivers of 

Europe. * • 

* See The Earth, the section entitled Rivers. . 



THUNDER-STORMS. . 305 



BOOK IV. — THUNDER. STOEMS, AURORAS, MAG- 
NETIC CURRENTS. 



CHAPTER XIX. 

HEIGHT OP THUNDER-CLOUDS, — DISTRIBUTION OF THUNDER-STORMS IN VA- 
RIOUS REGIONS OF THE EARTH. CAUSE OP THESE PHENOMENA. 

The condensation and the precipitation of watery vapor are always ac- 
companied by electrical phenomena; but this powerful force, which acts 
incessantly on the surface of the globe, does not manifest itself in a visi- 
ble manner in ordinary rains, for by them the atmospheric equilibrium is 
hardly disturbed. But when tfie clouds are suddenly condensed, and 
when the ground and the different strata of air are very different in tem- 
perature and electrical tension, harmony can only be re-established by vi- 
olent discharges, accompanied by lightning. It is then that we see in 
the sky, which is black with clouds, the magnificent spectacle of those 
dazzling flashes which spread in sheets or shoot in long zigzag darts. 
One instant the terrible light fills the sky, then space is covered anew 
with darkness, and we hear bursting from the gloom the immense voice 
of the thunder which reverberates in dull echoes from the clouds and the 
orround. In violent thunder-storms the deflagrations sometimes follow 
each other so closely that the horizon is lit up all round with one contin- 
uous flash, while crashes and long rollings of thunder echo from various 
points of the sky at the same time, and rain falls in torrents from" the rent 
and broken clouds. Often, too, these storms shower upon the ground a 
mass of hailstones formed of concentric layers of frozen water surround- 
ing a small crystal, sometimes very regular in form. Every one of these 
storms, however, differs in its proceedings. Some are simply passing phe- 
nomena, others are electric whirlwinds, or they may even be considered 
as real cycloneS. In these terrible tempests lightnings six and even nine 
miles long have sometimes been seen. 

The principal zone of thunder-clouds extends at a considerable elevation 
above the ground, as is easily ascertained on heights. " Mountains attract 
the thunder," say the proverbs of almost all nations ; and it is, in fact, on 
the gi-eat elevations of the terrestrial surface, where the clouds strike and 
are condensed into water, that the electrical discharges most frequently 
take place. Besides, isolated and pointed rocks must act as so many nat- 
ural lightning conductors, and they are consequently much oftener struck 
by lightning than the lower walls of the mountain gorges. It is to the 
repeated action of these phenomena that we must attribute the singular 

20 



306 



THE ATMOSPHERE AND METEOROLOGY. 



magnetic state of those rocks, near which the mariner's compass is dis- 
turbed, and takes, without any apparent rule, the most various directions. 
Forbes and Tyndall cite a remarkable example of this phenomenon on the 
Rieffel Horn of Monte Rosa at more than 9000 feet high. Humboldt has 
seen rocks split by the lightning at the summit of the mountain of Toluca, 
in Mexico, at 15,000 feet above the level of the sea. Messrs. Peytier and 
Hossard have observed some Pyrenean storms which were formed at still 
greater heights. In a general way we may say that the hdght of these 
electrical storms is that of the great " cumuli " from which they take their 
origin.* 

Thunder-storms, like simple rains, burst more frequently in the elevated 
gorges of mountains turned toward the sea than anywhere else. It was 
because of the numerous tempests which assailed the rough coasts of Epi- 
rus and Illyria that the Greeks made the Acroceraunian Mountains the 
seat of Jupiter, " the hurler of thunder ;" still these mountains are little 
visited by storms in comparison with several chains which rise in the 
tropical zone on the shores of the ocean, and transversely to the direc- 
tion of the rainy winds. Thus the Sierra Nevada of Sta. Martha, in Co- 
lombia, has a storm every day ; and the few 'travelers who climb one of 
these great peaks above the zone of tempests may expect, from two 
o'clock to four o'clock, to see the magnificent spectacle of a tumultuous 
sea of clouds, all trembling with lightnings, unroll beneath their feet. 




Western Europe. 
Central Europe. 

Naniber 

\ ^X1nte^ Spring SnmmerAutninnWnler 

Fig. 137.— Average Amount of Storms iu Europe. 

In general, thunder-storms are most numerous in a country where rains 
are most abundant. The zone of equatorial calms anqj^that of the mon- 
soons where moisture is precipitated in such considerable quantities, are 
also the regions of the earth where it thunders most frequently. At Ben- 
gal the annual number of thunder-storms is from fifty to sixty ; in the An- 
tilles, about forty are counted per year ; under temperate climates there 
* Becquerel and Ed. Becquerel, Elements de Physique Terrestre. 



DISTRIBUTION OF THUNDER-STORMS. 



30'; 



are only about twenty, and these occur almost always during the warm 
season. In Eastern Europe it is almost unexampled, so to speak, that 
they break out in winter. But on the western coasts of the continent, 
which are subject to the tropical influence of the Gulf Stream, these 
stormy conflicts of the air take place also in the cold season. It is a cu- 
rious fact that it is in winter that the greatest quantity of hail falls in 
Great Britain, In the direction of the poles the number of storms grad- 
ually diminishes. In the north of Europe thunder is a very rare phenom- 
enon, and it is even said that in Iceland and on the coasts of Spitzberg- 
en — that is to say, precisely* in those countries where the magnetic aurora 
shines — lightning has never been seen in the sky. As to the countries of 
the tropical zone which do not receive any rain, like the goast-line of Peru 
and Bolivia, it does not thunder there either. The lightnings which are 
sometigaes seen by mariners sailing toward the open sea from the coasts 
are merely reflections of those that escape from the clouds at hundreds of 
miles to the east, on the eastern slopes of the Cordilleras. 




Numbei- ^X^iter Spring Sununer Aixbumn ^^5nter • 
Fig. 138.— Proportion of Hailstorms during the Seasons in Russia and England. 

As the numbgr of tempests diminishes gradually from the equator to the 
poles, so are they reduced little by little in the open sea in proportion to 
their distance from the shores. This is a pretty general rule — at least in 
the seas of the torrid zone and the Antarctic Ocean. According to Arago 
and Duperrey, who have collected all the observations made before them 
on the tempests of the sea, no sailor has ever heard thunder in the middle 
of the South Atlantic, nor in the great ocean of the south between Easter 
Island and the island of the Antipodes. It is because of the relatively 
small number of storms breaking out on the open sea that ships, which 
attract lightning by the form of their masts, have been able to escape 
being struck. 

Taken as a whole, the thunder-storms of Western Europe follow the 
same general direction as the tempests, and often accompany them on 
their course. This is shown most clearly by the meteorological maps 



508 



THE ATMOSPKERE AND METEOROLOGY. 



of France, drawn up since 1865 at the Observatory of Paris. The storms 
are not there purely local phenomena, as was even recently supposed, but, 
on the contrary, they form part of the general system of atmospheric 
changes.* It is proved by thousands of observations made systematic- 
ally in different parts of the French territory, that almost all the thun- 
der-storms come from the ocean ; very often the inhabitants of the coasts 
hear the rumbling of the thunder several hours before the storm breaks 
over the continent. In the same way in Germany, and even in Russia, 
thunder-clouds from the enormous basin of evaporation of the Atlantic 
come from the west and south-west. 




Fig. 139.— Storms on the 9th of May, 1865. 

It is therefore in quite an exceptional manner that rapid ascending cur- 
rents, charged with moisture from the lakes and rivers, produce storms in 
the very interior of the continents. But on the various points of their 
path thunder-storms from the ocean are generally much modified by the 

* Atlas des Orages Redige par V Observatoire de Paris. 



COURSE OF THUNDEli-,'iTORMS. 



309 



medium through which they are propagated. Above regions differing 
from one another by the irregularities of the ground, nature of the soil, 
vegetation, and climate, the thunder-storms pass, by abrupt passages, from 
relative calm to fury; here the thunder rolls incessantly, and hail beats 
down the crops; there the clouds only discharge rain; still further, the 
wind drives the torn clouds before it without a single drop of rain fall- 
ing. It is because of these great inequalities in the advance of the tem- 
pests that it is often difficult to recognize a regular series in the disturb- 
ances which succeed each other over distant parts of the. same country. 




Pig. 140.— Storm in the Plaiu to the North of the Pyrenees. 

The secondary storms which are formed here and there on the track of 
the principal atmospheric current are the more influenced in their march 
by the accidents of the ground and the variations of temperature, the less 
considerable they are, and the nearer they approach to the terrestrial sur- 
face. They also present the greatest variety of speed, and deviate fre- 
quently from their normal direction, to spread along mountains, hills, or 
forests. Thus, as M. Becquerel has proved in his meteorological studies 
on the centre of France, the greater part of the secondary storms regular- 
ly follow the course of the great valleys like so many aerial rivers, super- 
imposed on the liquid rivers which roll below. When a thunder-storm, 
after having originated on a lateral plateau, directs itself obliquely to- 
ward a valley, it changes its course above the river, and never fails to 
follow its meanderings either up or down, as if it formed a bed for its 
own course in the great fosse of the valley. The storms which proceed 
at right angles to the direction of the river are the only ones which turn 
neither to the right nor to the left to enter the great depi-ession which is 
open to them, the force which tends to carry them along parallel to the 
valley not being powerful enough to cause them to deviate from their 
route. 

If the storms are attracted, so to speak, by the roads which the larger 
valleys present to them, it seems equally proved that they seek to avoid 
the forests. Thus the various currents of clouds charged with hail, »vhich 



310 



THE ATMOSPHERE AND METEOROLOGY. 



ravage more or less periodically the plains of the Loiret, pass round the 
forest of Orleans, or, at least, damage only its very edge. Whence arises 
this relative immunity of trees ? Do they retard the current of air by 
their crowded trunks, and thus force it to let fall its burden of hail out- 
side, and then to flow laterally, respecting the thick mass of the forest? 




Fig. 141.— Hailstorms of Orleans. The gray Tint indicates the Region affected by the Storms. 

Or do they act as lightning-conductors on the clouds, thus preventing the 
hail from being formed? These questions are still much discussed; but 
however it may be, it is certain that the forests often cause the hail to de- 
viate, and that the uprooting of trees often results in the modification of 
the regular course of the storm at the expense of agriculture.* The nu- 
merous meteorological maps drawn up by M. Becquerel and other learned 
men do not allow of a doubt that the zones in which hailstones most fre- 
quently occur are really modified in their extent by the distribution of 
forests over the territory. 

* Becquerel, Comptes rendus de VAcademie des Sciences, 1865, 1866, 1867. 



HAILSTORMS IN EUROPE. 



311 



Not only the form and direction of the valleys, as well as the greater 
or less extent of the forests, give to the ground the power of calling up 
or allaying storms ; but it seems also that the geological composition of 
the rocks exerts an influence of the same nature. Thus, to cite only two 
examples, certain masses of diorite in the Department of Mayenne dissi- 
pate or turn aside all the storms ; while above the iron mine of Grondone, 
in the Apennines, a cloud forms almost every day during the months of 
July and August, and regularly bursts in claps of thunder toward four or 




Fig. 142.— Hailstorms of the Lower Rhine. The part tinted indicates the regions of Hailstorms. 

five o'clock in the afternoon.* Nevertheless, these are phenomena for 
which no certainty is as yet obtained. According to M. Fournet, the sa- 
vant who has best studied the laws of the rains and winds in the basin 
of the Rhone, the nature of the rocks and vegetable soil, the extent of cul- 
tivated fields, pasturage, and forests, exercise but a slight influence on the 
distribution of storms; the direction and depth of the valleys, the height 
and precipitancy of the salient points of the earth, are much more impor- 
tant in this respect. 

* Blavier, Vicat, quoted by Zurcher and Margolle, Meteores, p. 119. 



312 THE ATMOSPHERE AND METEOROLOGY. 

■ This question of meteorology is still very obscure, as are those relative 
to the fall of hail. Why under temperate climates is the zone of hail, 
which forms above the plains, almost always narrower than that of the 
storm itself? Why is the fall of hailstones such a rare phenomenon un- 
der the tropics, at least in the regions of the plains? Why during a 
whole century has it only hailed once at Havana ? Science is not yet in 
a position to answer with certainty. In regard to the formation of hail, 
the theories are contradictory to each other; and it is asked how hail- 
stones, those heavy projectiles weighing as much as seven ounces to ten 
ounces, can be crystallized in the heights of the aii-, and most frequently 
in summer, a little after the hottest hours of the day. What is most prob- 
able is, that those whirlwinds which always occur when two opposite cur- 
rents meet are the great producers of hail. In consequence of the centrif- 
ugal force, the air is rarified in the centre of the whirlwind, drops of wa- 
ter are congealed, and whirl in the great eddy, while at the same time 
cold air from the upper frozen regions is sucked down the immense funnel 
which is formed in the midst of the clouds, and thus the hailstones revolv- 
ing in the vapors incessantly increase in bulk and number till they are 
dashed to the ground by the whirl of the gray clouds surrounding them. 
This theory, which is that of Mohr, Lucas, and Hann,* explains why hail 
is so rare in tropical regions, where the strata of frozen air are too high 
for the whirlwinds of clouds to be able to draw them down in their ed- 
dies. The appearance of the stormy nimbus, the small extent ravaged by 
hailstoi'ms, the oblique fall of the projectiles, together with the violence 
with which they strike the earth, and the gyratory direction taken by the 
corn thus beaten, are facts which give a great degree of plausibility to 
this hypothesis of the German savants. In any case, the power of the 
aerial currents, which are in strife during the formation of hail, must be 
truly formidable ; for certairf showers of hailstones are strong enough to 
form a kind of temporary glacier. On May 9th, 1865, the mass of hail- 
i?tones which fell on the meadows of Catelet formed a bed over a mile 
long and nearly half a mile wide, estimated to be equivalent to 700,000 
cubic yards. Four days afterward the hailstones had not disappeai'ed.f 

Many facts relative to the cause of storms are still unknown : no reason 
can be given for the fact that on the shores of the North Sea, of the Gulf 
of Bengal, and many other regions bordering on the ocean, thunder-storms 
almost always commence at the hour of high tide.J Another very strange 
phenomenon, as yet unexplained, is the appearance of those lightnings 
which dart from time to time from certain caverns in the cliiFs of the 
N^orwegian coast. Between Bergen and Trondhjem, on the shores of the 
.TOrend-fjord, rises Mount Troldjol, or the rock of wonders; from time to 
time, though more often when the weather is about to change, columns 
of flame and smoke, followed by peals of thunder, escape from a lateral 

* Zeitschrift der Meteorologie von Jelinek, No. 13, 1867. 

t Mariotti, Atlas de V Ohservatoire. 

X Prestel, Bastian, Hann, Zeitschrift der Meteorologie von Jelinek, No. 17, 1867. 



STRANOE ELECTRICAL PHENOMENA. 31 3 

tissure of this mountain. But the cavern in which these mysterious 
storms are developed is so difficult of access that no one has yet entered 
it. Nor has an attempt yet been made to explore another " laboratory 
of tempests," occurring in the southern of the two cliffs at the entrance to 
the Lyse-fjord. This perpendicular wall is 3600 feet in height,* and to 
reach the cavern it would be necessary to descend by means of ropes more 
than 1000 feet in the terrible abyss. From time to time, especially dur- 
ing a strong east wind, a flash of lightning is seen to shoot from the black 
rock, which expands and contracts alternately till it is finally lost before 
having reached the northern cliff. The sheet of fire revolves as it ad- 
vances, and it is to this rotatory movement that the apparent expansions 
and contractions of the lightning are due. Rapid detonations make them- 
selves heard Avith increasing force before the flame darts from the rock ; 
a violent peal of thunder accompanies it, I'everberating with long repeated 
echoes in the narrow glacier-formed corridor: one would think that a bat- 
tery placed in the cliff was cannonading some invisible foe concealed in 
the opposite wall. Such were the' strange phenomena of which the geo- 
graphical engineer Krefting was the witness in 1855, during a topograph- 
ical survey of the country. The inhabitants state that in fine weather, 
and when the wind has not blown from the south-east for several days, 
smoke of a yellowish gray color is seen to issue from the caverns and 
creep up the rock.f 

* See above, p. 130. ' ^ 

t Vide Kiisten von Norwegen. Ergdnzungsheft, Mittheilungen von Petermann, 1860. 



314 THE ATMOSPHEPE AND METEOROLOGY. 



CHAPTER XX. 

POLAE ATIEORAS. 

The violent tempests which are so frequent in the temperate, and still 
more so in the tropical regions, form a most striking contrast to the long 
and silent atmospheric disturbances which make themselves apparent in 
darts of flame over the polar heavens. These are the Aurora Australis 
and the Aurora Borealis. When hut slightly luminous, they appear as a 
whitish or vaguely illuminated cloud in the direction of the pole, though 
often the existence of these phenomena can only be recognized by the 
sudden variations of the magnetic needle. These almost invisible polar 
auroras are frequent in the temperate zones, where we very rarely can 
contemplate the sight of the sheets of flame and rockets which give such 
magnificence to the grand northern auroras. In Central and Southern 
Europe many persons jjass their lives without ever witnessmg one of 
these beautiful spectacles of nature. The only silent displays of terres- 
trial electricity which they have seen are those vague glimmers which 
often issue from the ground during dark nights. As Humboldt has ob- 
served, this telluric light is often sufficiently bright — especially in winter, 
when the ground is covered with snow — to enable one to discern the 
forms of objects at as great a distance as during twilight. 

It is to Scotland, the Shetland Isles, Scandinavia, North America, or, 
better still, to Lapland, the shores of Hudson's Bay, and the polar islands, 
whei-e long winter nights endure for several weeks, or even months, that 
we must go in order to contemj^late these vast auroral displays in all 
their grandeur. In 1838 and 1839 a French scientific expedition, encamp- 
ed on the shores of the Alten-fjord, under the seventieth degree of north 
latitude, observed during 206 days 153 auroras, not reckoning six or seven 
phenomena of this kipd which were doubtful ; and 64 of these took place 
during the period of 70 nights, which intervened between the 17th of Oc- 
tober, 1838, and the 25th of January, 1839; so that the members of the 
expedition came to expect the periodical return of these exhibitions as a 
matter of course. When the aurora was wanting, the sky was almost 
always covered in a great part with clouds. 

Auroras first appear as a faint glimmer on the northern horizon like an 
undecided day-break. A large dark segment of black clouds, in which 
Bravais believed he recognized the mass of fogs which brood in the dis- 
tance over the sea, spreads over the sky in the direction of the magnetic 
pole. Soon a curve of light shows itself above the thick stratum of va- 
pors like an immense arch, spi-eading from one end of the earth to the 
other. The light of a yellowish white hue gains rapidly in brilliancy, 
without, however, extinguishing the luminosity.of the stars which sparkle 



THE AURORA BOREALIS 3 15 

through it ; it flashes, vibrates, and moves like a flame shaken by the 
wind ; sometimes, too, it divides into symmetrical masses, appearing like 
the flaming openings of a building on fire, the fayade of which has re- 
mained dark. Often a second luminous arch, and a third, or even several 
other more concentric arcs of fire, form above the first, and stretch up to- 
ward the heavens. For some time these arches of light alone illuminate 
space ; then we suddenly see colored rays flash from the arches to the 
zenith, in convergent pencils, green at the base, golden yellow at the cen- 
tre, and a red purple at the extremity, succeeding each other regularly, 
thus adding to the splendor of the light by the most dazzling beauty of 
their colors ; and often, according to Hansteen, black or dark violet rays 
alternate with the rings of light, thus rendering them more brilliant by 
contrast. The beauty of the aurora borealis is due to the infinite varie- 
ty of its changing forms even more than to its various colors. Now the 
two ends of the arch rise off" the horizon, and the luminous sheet undu- 
lates and turns back upon itself like an immense friiiged drapery; now 
the sheaves of rays suddenly arrested seem to unite in a golden cupola ; 
often they are separated from one another as by columns of smoke, and 
the glimmering rays of the aurora are alternately extinguished and re- 
lighted. These rays, to which the Canadians give the name of " marion- 
ettes," or merry-dancers, vary incessantly in length and brilliancy ; the 
earth itself, being almost always covered with snow daring the time when 
the magnetic light is most frequent, appears now clearer, now darker, by 
contrast with the flaming raj's. At the magnetic zenith, toward which 
the southern pole of the needle is directed, the sky appears dark ; but all 
round it the divergent rays which come from the northern horizon, and 
spread farther and farther from each other toward the south, form a sort 
of crown. This is the most brilliant period of the phenomenon. After- 
ward the splendor of the arches and rays diminish gradually; they are 
seen to palpitate, so to speak, as if the stifled flame tried to revive, which 
is gradually extinguished, and there only remain here and there "auroral 
disks " emitting a feeble glimmer like the distant lightnings of a tempest ; 
and then there only remains a vague phosphorescence on the whitish cirri. 
Usually the magnetic aurora completely ceases before the first faint 
glimpse of dawn begins to show itself on the eastern horizon.* 

Most natural jDhilosophers assign a considerable elevation to the polar 
auroras. They think that these phenomena are generally produced in a 
very rarefied medium toward the upper limit of the atmosphere, and one 
is inclined to consider this opinion as very probable, seeing the analogy 
which exists between the brilliant colors of the arcs and rays of the auro- 
ra, and of those caused by passing an electric current through a vacuum. 
After having confirmed Hansteen's idea that the northern auroras are not 
arches of light, as they appear by an optical illusion, but really circles 
surrounding 'the magnetic pole, and radiating at the same time toward all 
the circumpolar regions of the Old and New World, Bravais attempted 
* Lottin, Bravais, Kamtz, Becquerel, Loomis, etc. 



316 



THE ATMOISPEEBE AND METEOROLOGY. 



to measure their height, and calculated that it is on an average 95 miles 
above the surface of the earth, Latei-, M. Elias Loomis, one of the most 
distinguished physicists of North America, compared and thoroughly dis- 
cussed all the observations recorded in various latitudes of the two mag- 
nificent auroras of the 28th August and 2d September, 1859, and the result 
of his researches tends also to prove that the mean elevation of the rays 
is very great. Thus, at the appearance of the former . aurora the lower 
extremity of the columns was formed at 46 miles high, while tlieir upper 




Pig 143.— Elevation and Bieadth of the Auiora Boiealis of 2i.th Auguat, lfc.59. 

extremity attained the enormous height of 530 miles. The rays of the 
latter aurora extended upward into the sky, from an elevation of 50 miles 
to 490 above the sea-level. By a like calculation of the height of thirty 
other auroras, it has been found that the extreme height reached by the 
rays is, on an average, 450 miles above the earth, and that the length ot 
these brilliant rays is ordinarily about 400 miles.* It is true that earlier 
observers have arrived at quite different results. Some even believed 
that, from the appearance of reflections in the clouds, certain auroras oc- 
cur in the lower regions of air at no greater elevation than half a mile 
* Smithsonian Institute, Annual Report for the year 1865, p. 218, and following. 



HEIGHT OF THE AURORA. 



31' 



or a mile. On the shores of Lake Scavig, in Scotland, rays have been seen 
to issue from a rock ;* but it is probable that these beams from below are 
secondary phenomena. However it may be, one can not doubt that au- 
roras have the atmosphere for their theatre, for they follow the general 
rotary movement of the globe in its direction from west to east. The 
following figure indicates, according to the observations collected by M. 
Loomis, the position and relative height of the aurora borealis of Sep- 
tember 2, 1859, which shone with such brilliancy above the United States 




gotes^x 












' ' ""^'J^^ 




Fig. 144.— Elevation and Breadtli of tlie Aurora Borealis of Id. September, 1S59. 

and Central America. The upper fringes of the most southern sheet ap- 
peared vertically above the ground in Florida at the latitude of 25° 15', 
and the general inclination of the aurora was precisely that which a mag- 
netic needle freely suspended would have had in the same region.f The 
aurora, which appeai'ed four days before, had its southern limit in Virginia 
toward 38° 50' of latitude. 

The inhabitants of the North relate that auroras are often accompanied 
with detonations ; nevertheless, in no case has a scientific observer ever 

* Thienemann, Wrangel, Struve, Farquharson, quoted by Kamtz, Lehrbuch der Meteorolo- 
gie ; Felix Foucon, Histoire du Travail, p. 79. t See below, p. 325. 



318 



THE ATMOSPHERE AND METEOROLOGY. 



noticed the least sound which seemed due to them ; for, as Becquerel has 
remarked, it would not be astonishing if the splitting of the plates of ice 
composing the cirri, under the influence of the currents which traverse 
them, caused a slight noise to be heard. It is, in fact, in an atmosphere 
full of ice-crystals that the aurora most frequently occurs, which can be 
observed immediately after the cessation of the phenomenon, by seeing 
that clouds formed of icy particles are exactly in the direction whence 
the most brilliant light flashed. As Loomis justly says,* when one sees 
the light flash, it is natural to listen for a report, and one often hears 
that which one wishes to hear. It is thus that the ancient Germans per- 
ceived the hissing of the sea when fhe setting sun, like a red-hot iron, 
sank into it. 

An aurora may last for a long time, even for a day or two, or even long- 
er; for during the whole week which commenced August 28th, 1859, this 
phenomenon endured with greater or less intensity over the United States. 



500. 




Jan^ Jteb^ March April Tfejr June July Aug*- Sept^ Oct^."" Nov^ I)ec'=.' 
Fig. 145.— Monthly Distribution of the Aurora Borealis (after Kamtz). 

In full daylight the disposition of the clouds and the restlessness of the 
magnetic needle revealed the invisible aurora. In 1786 Lowenorn even 
recognized after sunrise the luminous beams of an auroral light, so brill- 
iant were they; but it is almost always during the night that this phe- 
nomenon takes place. The colored rays which exercise such a great in- 
fluence on the movements of the magnetic needle ordinarily appear before 
ten o'clock in the evening, and are rarely perceived after four o'clock in 
the morning. Bravais aflirms that the auroras which he witnessed in his 
polar expedition commenced on an average about seven hours fifty-two 
minutes in the evening. It was then that the luminous arch extended 
over the sky ; soon after the rays darted towai'd the zenith, the auroral 
disks appeared, and toward half-past three in the morning the last glim- 
mers vanished. In the same way it is during winter, which is, so to speak^ 
* Aurora Borealis, Smithsonian Report for 1865, p. 222. 



DURATION OF THE AURORA. 



319 



the night of the northern hemisphere, that the auroras advance to a great- 
er distance to the south, and appear to the inhabitants of the temperate 
zone. The periods during which these magnetic disturbances most fre- 
quently occur are those of the equinoxes, at the commencement and end 
of the winter season. Meteoric phenomena of this kind are most scarce in 
the month of June. M. Bone, who has made a list of all the scientific ob- 
servations of auroras up to 1860, enumerates only seven for the month of 
June, while no less than 458 have been recorded in Mai'ch, and 498 in Oc- 
tober at the time of the equinoxes. The figure on opposite page may give 



October 




o^.J^ril 



Jiiljr 

Fig. 146.— Monthly Distribution of the Aurora Borealis (after Klein). 

some idea of the distribution of the auroras in the diflerent months of the 
yeai-. Figure 146, constructed on slightly different data, and according to 
a more logical method, as it represents the circle of the year, shows also 
that this is the average distribution of these aerial storms. 

It is probable, whatever the meteorologist Glaisher may say, that the 
magnetic auroras have also their periodicity, like all the other phenomena 
of nature. This is established by the catalogue of observations made in 
Europe and North America from the end of the seventeenth century to 
our own time. In 1697 the auroras were not at all numerous, but they 



320 



THE ATMOSPHERE AND METEOROLOGY. 



gradually became more numerous till 1728, and then diminislied. In 1755 
they were of very rare occurrence, but became more and more frequent 
toward the end of the century; in 1812 they were again at a minimum; 
but from the year 1825 they increased in number very rapidly, the aver- 
age rising from one per annum to thirty and forty in the same space of 
time. It would appear, from the discussion of these facts, that the cycle 
of auroras is one of fifty-eight, fifty-nine, or sixty years, and perhaps this 
period may itself be divided into six periods of ten years, corresponding, 
as Schwabe observes, with the regular variations oi, similar duration no- 
ticed in the number and size of the sun-spots ; thus the fluctuations of the 
magnetic storms constitute an astronomical phenomenon. The accompa- 
nying figure represents the series of auroras seen at New Haven, in Con- 
necticut, during the seventy years from 1785 to 1854, comprising an entire 
period. 

^5- 



So- 

45- 

to- 
so- 

SB 

gO- 

15- 



/Kl 1 /L 




^ fears 1784 12»4 I80i 1814 1824 

Fig. 147.— Auroras observed at New Haven, Connecticut, United States, 1784-1854. 

It is difiicult to explain now why the aurora appears more frequently 
in certain places of the Old and New World than in other parts situated 
at an equal distance from the magnetic pole. But it is incontestable that 
this latter point is not distant from the centre whence the auroral light 
radiates. In our hemisphere the, culminating point of the luminous arc is 
found toward the direction of the peninsula of Boothia Felix, where Ross 
saw the southern pole of the magnetic needle turn directly toward the 
centre of the earth. In Norway one sees the auroi-a borealis in the north- 
west ; in Greenland, directly to the west ; at Melville Island, Parry viewed 
it on the southern horizon. It must not be thought, however, that these 
magnetic storms are very frequent in the high circumpolar regions; on 
the contrary, they are rather rare there, to judge from the accounts of 
travelers who have advanced farthest to the north. Hayes, during his 
stay in Smith's Strait, only saw three phenomena of this kind. In this 
northern space, which is destitute of auroras — that is, in Southern Green- 



AURORA BOREALIS. 



321 



land, the Polar Archipelago, the north of Siberia and Spitzbergen — there 
is a zone of three hundred miles in diameter, where about forty times ev- 
ery year these northern lights are visible. The wider zone, which com- 
prehends Hudson's Bay, Labrador, Iceland, and the north of Scandinavia, 




Fig. 148.— Circumpolar Zone of the Aurora Borealis. 

is richer, for eighty of them occur on an average yearly. Farther south 
extends a third zone, where these magnetic disturbances become less and 
less numerous; finally, in temperate regions these phenomena are rare, 
and toward the Tropic of Cancer they are almost unknown. At Havana, 

21 



322 '^™ ATMOSPHERE AND METEOROLOGY. 

only six auroras have been seen on the northern horizon in one hundred 
years.* These magnetic storms very frequently extend over nearly all 
the northern hemisphere at the same time, thus being very dilFerent from 
thundei'-storms, which are usually confined to limited areas. The aurora 
of 28th August, 1859, was visible from California to the Ural Mountains, 
over a space of moi'e than one hundred and fifty degrees of longitude. 
That of four days later was seen at the Sandwich Islands, in the whole 
of North America, and in Europe ; while at various stations in Siberia 
where the sky was cloudy, the '"Variations of the magnetic needle testified 
to the atmospheric disturbances. It was on this occasion that the simul- 
taneous appearance of the aurora on the two sides of the earth was first 
noted, both in the skies of the northern*hemisphere, as we^l as above the 
Cape of Good Hope, Australia, and South America. At the same instant, 
in Labrador, at Philadelphia, Edinburgh, Algeria, and Valparaiso, lumi- 
nous streaks were seen to dart from the polar regions ; the storm was vis- 
ible over more than half of the planet. Thus the theory of the meteor- 
ologists, that the northern and southern auroras occur at the same time 
in both hemispheres under the influence of the same current, was con- 
firmed. Of thirty-four auroras observed at Hobart's Town, in Tasmania, 
between the years 1841 and 1848, twenty-nine coincided with the occur- 
rence of the same phenomena, either in Europe or in North America, and 
all were marked by magnetic perturbations at the opposite pole. The 
fact, noticed by Forster, has since been confirmed by others, that the 
northern and southern auroras present remarkable contrasts in the color 
of their rays, the light of the latter being of a pale blue, and less colored^ 
than that of the arctic regions, thus forming a parallel to the way in which 
the hues of the rays of light differ at the two poles of an electric current. 
It may be considered certain that the extremities of the earth are in in- 
timate connection with one another through the electric and magnetic 
currents continually circulating between them, both in the air and the 
mass of the globe. The researches of M. Becquerel and other natural phi- 
losophers have shown that it is probable that the superior strata of the 
atmosphere are almost always charged with positive electi'icity, and the 
warmer strata reposing on the surface of the land and of the sea, with the 
opposite kind, of electricity. In consequence of the enormous evaporation 
from seas under the tropics, the moisture charged with positive electrici- 
ty, rising to the upper atmosphere, maintains it in a state of constant ten- 
sion; but violent thunder-storms, accompanied by very abundant rain, 
constantly tend to restore the equilibrium. Away from the tropical zone, 
the higher and lower strata, less strongly electrified, no longer by sudden 
discharges, but by the silent action of the polar auroras, the two contrary 
electricities meet and are neutralized. Such is the theory. In any case, 
it is certain that the auroras are electrical phenomena, since they act on 
the wires of the telegraphs like voltaic batteries, and since the colors of 
the arcs, beams, and auroral rays are precisely those of the ordinary elec- 

* Elias Loomis, Aurora Borealis, Smithsonian Report for 1865, p. 215. 



AURORAS. 323 

trie spark passing through rarificd air. At the ^|^e time auroras are 
magnetic phenomena, as is proved by their powerful action on the move- 
ments of the needle. Though produced in the atmosphere, and always 
accompanying the globe in its diurnal rotation, they are also very prob- 
ably astronomical phenoniena, obeying in their successive periods the cy- 
cles of the sun. Solar attraction, magnetism, electricity, are all converti- 
ble forces which work in concert to modify incessantly, and then to re-es- 
tablish, the equilibrium of the atmosphere. 






324 THE^TMOSPHEBE AND METEOROLOGY. 



V 



CHAPTER XXI. * 

TEEEESTEIAL MAGNETISM. — DECLINATIOlSr, INCLINATION, AND INTENSITY OF 
THE MOVEMENTS OF THE NEEDLE. — MAGNETIC POLES AND EQFATOE. — 
ISOGONAL LINES, AND THEIE SECULAE ANNUAL AND DIUENAL VAEIATIONS, 
— ISOCLINAL LINES, — ISODYNAMIC LINES. , 

The incessant mobility so characteristic of all the phenomena of cli- 
mate is most especially manifested in the perpetual oscillations of the 
electric currents. Magnetism — this force as mysterious as the nervous 
fluid of organized bodies, in its invisible undulations vibrating from the 
poles to the equator — transforms this planet into a gigantic loadstone. 
The heat of the sun, which gives life to our globe, causes a continual 
tremor in the crust of the earth ; currents of electricity (whose incessant 
movement from east to west in an opposite direction to the rotation of 
the globe, was discovered by Ampere) vibrate round the terrestrial sur- 
face like an immense coil, and maintain between the two poles a mag- 
netic activity exactly similar to that which is produced in an induction 
coil.* All bodies are mo% or less influenced by these currents, and 
would arrange themselves in certain regular directions did not the bulk, 
weight, and cohesion of their particles hinder them from obeying the 
force acting upon them. The magnetic power of the earth is estimated 
by Gauss at 8464 trillion times that of 'our strongest artificial magnets, 
and yet this immense power has only been known for a comparatively 
short time. It was only in the year 1700 that Halley drew the first mag- 
netic chart, and it is scarcely seven hundred years since the sailors of 
Amalfi, Provence, and Liguria learned from the Arabs, or discovered for 
thems^ves, the movements of the magnetic needle, and this was the ear- 
liest recognition of this magnetic current pervading every atom of the 
planet. The Chinese navigators had known the ren^arkable properties of 
the compass for more than two thousand years before this. 

In the earliest times it was believed that the needle pointed constantly 
toward the polar star, or rather toward the pole of our planet ; but the 
mariners who ventured as far as the Canaries and Iceland, or even thosfe 
who confined their voyages to the Mediterranean, ascertained that the 
point of the compass did not invariably indicate the north, and that it 
diverged according to the latitudes, by a greater or fewer number of 
degrees, to the right or left of the normal direction. In 1268, Pierre 
Pelerin de Maricourt observed that it pointed seven and a half degrees 
toward the east at Lucera, in Southern Italy.f Columbus, on the voy- 

* Barlow, Ampere, Becquerel, Sabine. See, also, les Phenomenes de la Physique, by Ame'- 
de'e Guillemin, pp. 702, 703. 

t Detvezac, Bulletin de la Societe de Geographic, 1859. 



MAGNETIC VABIATIONS. 325 

age in which he discovered the New World, also observed that the vari- 
ation of the compass was several degrees to the west of the astronomical 
jiole ; and it is said that he was obliged to re-assure his sailors, who were 
alarmed by this unexpected phenomenon. Finally, the expeditions of 
Magellan, Drake, and other circumnavigators of the globe, established 
the greatest east and west variations of the needle from the north pole. 
These variations are known under the name of declination. 

The deviation of the needle is not the only fact showing the magnetic 
action of the earth. In 1576 the Englishman Norman first noticed that 
the needle did not occupy a horizontal-position in the latitude of Europe. 
On ascending toward the north magnetic pole, the northern end of the 
needle dips more and more to the ground, and directly over the pole it 
becomes vertical ; while on the contrary, as we descend to the south, the 
needle becomes less and less inclined to the surface, till, on reaching an 
imaginary line called the magnetic equator, it is parallel to the ground. 
Beyond this it inclines more and more in the reverse direction, till, on 
arriving at the southern magnetic pole, the needle again becomes ver- 
tical, though now of course with its southern pole toward the earth : this 
is the phenomenon designated by the name of inclination. 

Nor is this all : if we cause the needle to diverge from its noi'mal di- 
rection, in returning to it it oscillates moi"e or less rapidly according to 
the part of the earth where we happen to be. These oscillations, analo- 
gous to those of the pendulum, reveal the greater or less intensity of the 
currents, according to the distance from either pole, just as the extent of 
declination and inclination varies. These local differences, however, are 
by no means permanent. The direction and force of the magnetic cur- 
rents which are produced on the surface of the planet change continually 
from hour to hour, from day to day, from year to year, and from cycle 
to cycle, conformably to laws of periodicity ; but science as yet has not 
discovered all the elements. Among the grand manifestations of planet- 
ary life, of fluvial and marine currents, of the weight of the atmosphere, 
of the pressure of the vapor of water, of the alternations of the wind, of 
the variations of the climate, there are no phenomena which are more rap- 
id and changeable in their alterations than those of terrestrial magnetism. 

What is the probable cause of those currents which vibrate around the 
earth, and by which the compass is incessantly agitated, like the weather- 
cock under the pressure of the winds ? The cause must be sought for 
not only in the movements of the earth, but equally in those of the sun, 
that great source of terrestrial life. The contrasting masses of earth and 
water, so unequally distributed in the two hemispheres, the diiference of 
temperature between the aerial strata, the diurnal rotation of the planet 
around its axis, its annual revolution around the sun, the different rate 
of motion of the various parts of the surface of the globe between the 
equator and the poles, the increase or diminution of its rapidity as it ap- 
proaches or retires from the sun, the rotation of the sun, and finally the 
various periodical phenomena to which it is subject, its movement in 



326 THE A TMO SPHERE AND METEOR OLOGY. 

space toward unknown regions of the heavens, the approach of a per- 
turbing planet, every thing, even the friction of the earth on the vapors 
which surround it, incessantly develop the magnetic energy of the globe, 
as an immense coil traversed by most powerful electric currents would 
do. In the ground which seems so impassive, but where so many germs 
give birth to life, whence so many wonders spring, the mysterious cur- 
rent circulates without ever resting, like an inexhaustible river. Under 
the influence of the sun, it hastens or slackens its speed, moves in one di- 
rection or the other, and travels over the circumference of the globe, its 
equator and its poles. It obeys unceasingly the harmonious laws of na- 
ture, while only seeming to act capriciously because of the manifold in- 
terruptions causing the apparent in-egularity in the succession of its peri- 
odicities. Just as the fine magnetic needle trembles and shakes like an 
affrighted creature in its box suspended at the ship's helm, so all over the 
earth magnetic currents oscillate and move untiringly ; directly obeying 
the cosmical influences which make themselves only slowly felt on other 
functions of the globe, they may rightly be compared to the nervous 
phenomena in the animal organism. In consequence of their continual 
vibratory motion, the magnetic currents can not be clearly traced on the 
map, and we must always confine ourselves to indicating their mean di- 
rection. There are not two instants in the year when the movements of 
the needlg are identical on the surface of the earth. 

The poles toward which the compass points in the two hemispheres 
stray constantly around the astronomical poles of the planet, and it is 
never at the same point that their precise position must be sought for. 
In 1832 Captain John Ross, then sailing in the midst of th'fe polar archi- 
pelago of N'orth America, arrived in the neighborhood of the north pole 
of the compass, since the point of his instrument was directed almost ver- 
tically to the earth. This point, toward which all the magnetic currents 
of the northern hemisphere then converged, was situated in the peninsula 
of Boothia Felix, nearly twenty degrees to the south of the terrestrial pole 
(70° 5' N.), and at more than ninety-nine degrees to the west of the merid- 
ian of Paris ; but since that epoch it has probably moved a few degrees to 
the east. The magnetic pole of the south has not been discovered by any 
navigator up to the present time. But according to the calculations of 
Duperrey, Gauss, and other savants, it would probably be found at four- 
teen degrees fifty-five minutes from the Antarctic Pole to the south of the 
continent of Australia. The two points of attraction of the magnet are 
thus each situated at the meridian of a group of continents ; but they are 
not antipodal to one another, since they ai'e found in the same hemisphere 
' separated from one another by an arc of little more than one hundred 
and sixty-one degrees — twenty-nine degrees less than the semi-circumfer- 
ence. As to the magnetic equator, which is the line where the needle 
keeps perfectly horizontal to the surface of the earth, it is no more to be 
confounded with the equator of rotation than the magnetic poles with the 
extremities of the planetary axis. It follows a curved line which cuts the 



THE MAGNETIC POLES. 327 

terrestrial equator to the cast of the Carolinas, traverses the islands of 
Sunda, Hindoostan, Ethiopia, and Soudan, then passes to the south of the 
equinoctial line not far from the island of St. Thomas, and lies in America 
above Brazil and Peru. We may say generally that the magnetic equator 
curves toward the north in the continents of the Old World, and toward 
the south in the New World. At the present time this line is slowly mov- 
ing its points of intersection of the terrestrial equator from east to west. 

The*two magnetic poles occupy in relation to the earth's axis a position 
quite oblique, since one is situated in the American polar archipelago, 
while the oth^r is found under the meridian of Australia. It results from 
this, that the currents are themselves propagated obliquely to the surface 
of the globe. Instead of advancing in the direction from north to south, 
the mysterious force moves according to curves not parallel, which on the 
Atlantic face of the earth bend toward the west, and on the opposite side 
for the most part diverge toward the east. The lines of separation between 
these two zones of western and eastern declination are the only parts of 
the earth where the compass points directly to the north. In order to in- 
dicate clearly the average direction of the magnetic needle for any year 
whatever in various countries, other lines, called isogones, are drawn on 
the map to the right and left of those marking no declination, where the 
compass forms one and the same angle with the terrestrial meridian. 
These curves, connecting all the points of the earth where the mean in- 
clination of the needle remains sensibly equal, are much less regular than 
the magnetic meridians. Some are directed from the north to the south, 
others run partly from the east to the west ; others, again, bend in the 
form of circles and ovals. 

At present, the line without declination which traverses the ancient 
world passes to the east of Spitzbergen, touches Russia in the environs 
of Archangel, gains the Caspian depression by the valley of the Volga, 
crosses Persia obliquely, then, after having coasted Hindoostan and the 
islands of Sunda, as if to mark the general outlines of the Asiatic conti- 
nent, it is directed abruptly toward the southern magnetic pole across the 
centre of Australia. To the west of this line, as far as the other side of 
the shores of the continental group which constitutes Europe and Africa, 
the declination of the compass toward, the west increases gradually, and 
then diminishes above the basin of the Atlantic, and is reduced to zero on 
the eastern coasts of the New World. The second line without declina- 
tion, which one might call the American line, descends from the magnetic 
pole to the west of Hudson's Bay, traverses the great lakes, passes the en- 
virons of Philadelphia and Washington, and then curves round the An- 
tilles, as the other line without declination is curved around the archipel- 
ago of Sunda, and cuts the extremity of Brazil from the mouths of the 
Amazon to Rio de Janeiro, and crosses the Atlantic toward the south 
pole. To the Avest of this line the deviation of the compass becomes 
easterly, increasing rapidly above America, then much more slowly across 
the Pacific, and diminishing to the east of China and Siberia, so as to in- 



328 THE ATMOSPHERE AND METEOROLOGY. 

close a kind of magnetic island where the declination is western, as in the 
basin of the Atlantic. Whatever may be the partial irregularities of these 
two zones of different variation, it is impossible not to be struck by their 
general agreement with the most salient features of the planetary surface. 
The basins of the Atlantic, the Mediterranean, and the Indian Ocean cor- 
respond with the western declination, and the Pacific corresponds with 
the eastern declination. Four continents — Asia, Australia, North and 
South America — belong to this latter zone ; while Europe and Afric^ form 
part of the zone of western declination. 

During the course of centuries the system of isogonal lines moves very 
rapidly in certain countries. In the seas of Spitzbergen to the west of the 
Antilles, in various regions of China, the mean direction of the needle has 
not varied in a perceptible manner for a century ; but it is not the same 
in Western Europe._ At Paris, at the time of the first regular observations 
on terrestrial magnetism, the declination of the compass was easterly ; it 
even reached, in 1580, 11° 31' to the east of the meridian. In 1663 the dec- 
lination existed neither in one direction nor the other ; the magnetic nee- 
dle was directed exactly toward the north. From that time the declina- 
tion toward the west continued to increase during more than a century 
and a half, till 1814, when the angle formed by the needle with the terres- 
trial meridian was not less than 22° 34'. Since then the needle has retro- 
graded toward the meridian, and in the year 1864 the angle was only 18° 
30' ; the recoil is thus, on an average, nearly five minutes per year, but it 
changes in a very irregular manner, for in cei'tain years the western decli- 
nation has suddenly increased again. We can not doubt that these secu- 
lar oscillations of the magnetic current make part of a cycle, the duration 
of which corresponds with that of some great astronomical phenomena. 
According to M. Chazallon, this period would be for Paris 488 years, and 
the magnetic needle would be again directed exactly toward the north in 
the year 2151. The line without declination moves little by little from 
the confines of Russia, and will successively traverse Poland, Germany, 
and France ; then passing above the Atlantic, it will later commence its 
return toward the east. Notwithstanding this secular balance of the 
magnetic forces, it is probable, however, that as a whole the currents never 
end by following exactly the same directions on the surface of the earth : the 
poles, the equator, the meridians moving incessantly, the net-work of mag- 
netic lines changes eternally like the relative position of the stars in space. 

While this long secular variation is accomplished, the needle is ever ag- 
itated by oscillations of shorter periods. Those which are completed in 
the course of a year are evidently connected with the position of the earth, 
relatively to the sun, for its various phases coincide with the equinoxes and 
the solstices. In Western Europe, as Cassini first ascertained, the compass 
gradually approaches the meridian, advancing toward the east, during the 
period which elapses from the equinox of March to the summer solstice ; 
then the magnetic needle again advances toward the west ; but slackening- 
its march little by little, it is only at the end of winter that it attains its 



Tlic ()r,.;in A-,- 



ISOCONIC & 




EugraA'CcLby-tphard. 



HARPER, fi: B 



:LINI C LINES. 



PL. XV. 




NEW yOB.K 



ISOQONAL AND ISOCLIXAL LIXES. 329 

f^reatest declination toward the west ; the return to the point ot depart- 
ure employs three-quarters of a year. In America the progress is ditter- 
ent, which doubtless results from the difference of declination. The total 
extent of the annual variations presents a great irregularity: in 1784 it 
was about twenty minutes at Paris.' 

The diurnal variations differ also on all points of the earth. In France, 
where the amplitude observed oscillates between five and twenty-five 
minutes, the needle moves from east to west between eight o'clock in the 
morning and one o'clock in the afternoon ; it then returns to the east, 
and toward ten o'clock it occupies nearly the same position as in the 
morning. In countries near the northern pole the extent of the diurnal 
variations is generally greater than in the temperate zone ; in the torrid 
regions, on the contrary, these variations are slighter, while in the south- 
ern lands the diurnal movements become more and more considerable 
toward the south. As there they occur in the inverse order to those 
observed in the north, it is probable that the two hemispheres with op- 
posite variations are separated from one another by a line where the 
compass remains immovable ; however, this equator, without variations, 
has not been yet discovered with certainty, and in all probability would 
not agree with the magnetic equator. 

In the same way as isogonal lines have been traced on the globe to in- 
dicate the declination of the compass in different years, so by the isoclines 
succeeding one another on each side of the magnetic equator, those parts 
of the earth are indicated where the magnetic needle dips toward the 
ground at the same angle. These isoclinal lines are in general more reg- 
ular in their curves than the isogonal lines ; but they also are influenced 
by the forms of the continents. It is principally in the northern hemi- 
sphere that this difference is shown. Thus the isocline of fifty degrees 
coasts the shores of Central America, then, after having crossed the basin 
of the Atlantic, traverses obliquely the depressions of the Sahara, the 
Eastern Mediterranean, the Caspian, and turns northward round the great 
mountains of Thibet. The isoclinal line of seventy degrees is developed 
off the western shores of North America from the peninsula of Alaska to 
the coasts of the Oregon, while in the Old World it follows the depres- 
sion formed by the Channel, the North Sea, the Baltic, and the Gulf of 
Finland. Finally, the line of eighty degrees follows at a distance the po- 
lar shores of America, runs afterward along the eastern coasts of Labra- 
dor and Greenland, and bends in an immense curve round Scandinavia. 
Like all the other magnetic phenomena, the inclination is subject also to 
incessant variations, periodical and accidental, but these variations have 
been less studied than thqse of declination. At Paris the needle has be- 
come less and less inclined since 1671, when it dipped seventy-five degrees, 
while in 1864 it was only 66° 3'; the annual diminution has thus been a 
little more than three minutes. Observations made at London, and in 
several other towns of Western Europe, lead us to the same result. As 
to the monthly variations, they are less relatively than those of declina- 
tion ; it is in summer that they have the greatest amplitude. 



330 



THE ATMOSPHERE AND METEOROLOGY. 



60 SO 



30 60 S>0 IZO 150 IBO 



s] L-^A te\c It t 




Fig. 149.— Isodynamic Lines. 

The isodynamic lines — that is to say, those which unite the points of the 
earth where the movements of the magnetic needle have an equal intensi- 
ty — for the greater part resemble in their curves the isoclinal lines ; nev- 
ertheless, they do not coincide with them. The dynamic equator — a line 
where the intensity of terrestrial magnetism is manifested with the least 
force — is also inflected in the southern hemisphere, traversing Peru and 
Brazil not far from Rio de Janeiro, and then ascending obliquely by the 
African continent toward the southern peninsulas of Asia and the archi- 
pelago of Sunda. On this equator the movement's of the needle are slow- 
est in the Atlantic off the Brazilian coasts. On each side of the line of the 
least force, the magnetic intensity increases toward the north and south, 
but in an unequal manner, since the isodynamic line of Florida bends to the 
north as far as Scandinavia, and that of South Carolina traces the outline 
of the American shores, and passes into Greenland. In the southern re- 
gions there only exists a single dynamic pole, situated at more than six- 
teen degrees from the planetary pole, in the neighborhood of the icy 
mountains discovered by Sir James Ross. It is there that the move- 
ments of the compass have the most intensity, and they are nearly three 
times more rapid than in the Brazilian seas. In the north there are two 
dynamic poles — one to the west of Hudson's Bay, the other to the north 
of Siberia, not far from the mouths of the Lena. In the same way as the 
isothermal lines, with which they have besides ^ great analogy, the lines 
of equal intensity have their two poles, occupying a symmetrical position 
— the one to the north of the Old World, the other to the north of the 
New. Thus, as Dnperrey remai'ks, this resemblance of the isothermal and 
isodynamic lines is a proof of the intimate connection which exists be- 
tween terrestrial magnetism and temperature. 



SOLAR HEAT. 331 



BOOK v.— CLIMATES. 



CHAPTER XXII. 

SOLAR HEAT. — lEEEGULARITIES OF LOCAL CLIMATES. — EQUALIZATION OF 
THE TEMPERATURE BELOW THE SURFACE OF THE GROUKD. 

All the facts of physical geography, the relief of continents and islands, 
the height and direction of the systems of mountains, the extent of for- 
ests, savannas, and cultivated lands, the width of valleys, the abundance 
of rivers, the outline of the coasts, the marine currents, winds, and all the 
meteoric phenomena of the atmosphere, vapors, fogs, clouds, rains, light- 
nings and thunders, magnetic currents, or, as Hippocrates said more brief- 
ly, " the places, the waters, and the airs," constitute in their connection 
with longitude and latitude what is called the climate of a country. 

The most important climatic phenomena are those of temperature, for 
it is to heat that most of the meteoric phenomena, in their various alterna- 
tions on the surface of continents and seas, are due. It is the overheated 
regions which put in motion the whole system of atmospheric currents, 
and it is they too which give to the winds the moisture destined to be 
dispersed in clouds and to fall far away in snow and rain. By their ac- 
tion on the earth and on the waters, the rays of the sun give the first im- 
pulse to all that moves on the surface of the globe. It is on this lumi- 
nous body that the life of our planet depends. 

The earth has, it is true, its own heat, like all bodies in space ; but 
whatever may be the unknown heat of its deeper Strata, that of the sur- 
face results solely from the great source of heat, the centre of our planet- 
ary system. When the sun rises above the horizon, the earth is warmed 
by its I'ays, but cools during the night by the radiation into space of the 
heat received during the day. The oscillations of relative heat and cold 
that we experience from day to night, and from summer to winter, all de- 
pend on the laws regulating the absorption and radiation of heat given 
off by the sun to the earth, or by the earth into interstellar space. It is 
these incessant alternations that the thermometer measures, since the 
heat of the air and the ground vary at all times and in all places; the 
series of temperatures which succeed each other in various localities, or 
even in one single place, become, so to say, infinite ; and if we wish to 
keep an account of the phenomena of heat and cold, it is necessary to ob- 
tain, by comparison of instruments at regular hours and periods, the aver- 
ages of diurnal, monthly, and annual temperature. This is one of the 
most difiicult tasks, for we must first remove all possible chances of error, 



332 TEE ATMOSPEEEE AND METEOROLOGY. 

and choose for the place of observation precisely one where the indica- 
tions of the thermometer are never modified by special causes, such as 
currents of air or radiated heat. The disturbing influences are so numer- 
ous that we are not yet sure ofhaving determined exactly the true aver- 
age temperature of a city like Paris, where millions of observations have 
been made. M. Renon even afiirms that for a hundred years meteorolo- 
gists have always given by mistake a temperature too high by almost two 
degrees Fahrenheit to the atmosphere of Paris. The use of automatic 
instruments which trace on paper, either by a pencil or by photography, 
the continuous series of curves produced by the oscillations of tempera- 
ture will diminish many probable errors, and singularly facilitate the com- 
parison of all the results obtained in diiferent localities. 

If the earth were a globe of perfect regularity, presenting on its sur- 
face no contrast of land and sea, plateaux and plains, snow and verdure, 
and keeping always at the same distance from the sun, a natural distribu- 
tion of climates would be established over the whole circumference of the 
earth, and one could exactly measure the degree of heat by the latitude. 
At the equator the temperature would be at its maximum, and from each 
side of this line decrease to the poles ; thus, as the mathematician Lam- 
bert calculated, the total quantity of heat received as 1000 under the 
equator would not be more that 923 under each tropic, and 600 under the 
polar circle. 

But the earth is not an accurate sphere, lighted in an always equal 
manner by the rays of the sun. It is illuminated in a different manner 
according to the seasons ; and the features of its surface, harmonious as 
they may be as a whole, have not the perfect symmetry of geometrical 
figures. From this results an infinite variety of climate. One country 
near the polar circle receives more warmth than another situated at a less 
distance from the tropics ; one region of the temperate zone is hot, in 
comparison with certain spaces in the equatorial zone. The temperature 
continually varies, oscillates, and changes under the action of winds, cur- 
rents, meteoric phenomena, and vegetation ; and when indicated by lines 
on the surface of the earth, an inextricable net-work is formed of which 
we can only recognize the principal traits. Every season, every day, ev- 
ery minute still adds to the entanglement of these various temperatures, 
for nowhere do the periodical evolutions of local climates resemble each 
other in a perfect manner. In mountainous districts especially, the least 
difference of exposure or height causes the temperature of two neighbor- 
ing places to vary as much as if they were separated from each other by 
hundreds of miles. Beside the wintering towns on the coast-line of Pro- 
vence and the maritime Alps, Cannes, Antibes, Villefranche, which are 
well sheltered by an amphitheatre of hills, the sterile valleys of the Var, 
the Loup, and the Siagne open, like fractures of the terrestrial crust, mak- 
ing a passage for the terrible mistral, which formerly, they said, contrib- 
uted more than Marius to chase the Cimbri from Gaul. The various lines 
of equal temperature which meteorologists have attempted to trace upon 



EQUALIZATION- OF UNDERGROUND HEAT. 333 

maps can never indicate more than general averages, through all the ex- 
treme lines moving incessantly from one side to the other like vibrating 
cords. And if the mean temperatui'e of a single place is so diflScult to 
know in an exact manner, how much more difficult to determine with pre- 
cision for the whole of a country, the general climate resulting from the 
combination of all the particular climates. 

Numerous observations made in different parts of the earth have dem- 
onstrated that the mean temperature, so difficult to ascertain with cer- 
tainty on the surface, is constant at a variable dejDth in the earth itself 
For as the solid strata composing the exterior of the globe conduct heat 
but very slowly, neither the solar influence can penetrate far inward, nor 
the internal heat radiate outward ; wherefore the variations of atmos- 
pheric temperature must be gradually diminished, or even entirely oblit- 
erated, at a certain distance from the surface. On an average, the heat 
of the day is propagated Avithin the ground so slowly that in nine hours 
it only traverses the first superficial layer of one foot in thickness. At 
depths varying from two to five feet, all the diurnal variations of heat 
completely disappear in the temperate zone. The annual variations, much 
more durable in their eflects, penetrate to a greater depth; but, in conse- 
quence of the earth being so bad a conductor of heat, it is found that at 
a few yards below the surface the order of the seasons is changed. The 
summer heat, so much retarded as it penetrates into the ground, only 
reaches the layers from twenty to twenty-five feet deep on the return of 
winter. On the other hand, the cold does not make itself felt in these 
depths till the middle of summer. The surface temperature takes no less 
than a whole month to traverse a layer of earth three feet thick, and, in 
so slow a passage, it ever tends to approach the annual average. At 
Brussels, the maximum heat having been felt on the surface on the 22d 
of July, only attained the depth of twenty-six feet on the 12th of Decem- 
ber following, one hundred and forty-seven days later ; in the same way, 
the interval between the cold on the surface on January 23d and that of 
the deep stratum on June 18th was one hundred and forty-three days; 
while the total annual variation of the temperature, which is about thirty- 
five degrees on the surface in this town, is less than two degrees at twen- 
ty-six feet below. * 

The complete neutralization of the influence of the seasons occurs at 
different depths. In the cellars of the Observatory of Paris, situated at 
ninety feet below the ground, the temperature is constant, and is always 
maintained at fifty-three degrees. On an average, it may be considered 
that in the north of Europe all the exterior influences of heat and cold 
have completely disappeared at seventy-eight feet below the surface. The 
better conductors the underlying beds are, and the more porous they are, 
allowing air to penetrate from the surface, the greater and more rapid are 
the penetration and radiation of heat. Experiments made at Edinburgh 
by Forbes show that carboniferous sandstone is one of the rocks which 
best conducts heat, for the equilibrium of temperature is only found at a 
depth of one hundred and five feet. In countries where the annual dif- 



334 



THE ATMOSPHERE AND METEOROLOGY. 



ference between the heat of summer and cold of winter is very great, it is 
relatively ver}^ low in the ground that we must search for the point where 
all the annual variations are neutralized. On the other hand, in those 
countries where the temperature of the vai'ious seasons hardly differs, it 
is only about a foot from the surface that the equalization of the annual 
temperature is established. M. Boussingault has ascertained that, in or- 
der to know the annual temperature of New Granada and Ecuador, it is 
sufficient in certain places to introduce the thermometer from one and a 
half to two feet into the ground. Under the polar climates, where the 
mean temperature of the atmosphere is below freezing-point, the few ob- 
servations that have been made seem also to establish the fact that the 
zone of neutralization of exterior influences is nearer the surface than un- 
der temperate climates : in certain parts of New Britain it is said to have 
a depth of only nine to fifteen feet.* At Yakutsk, where the thermomet- 
ric average is twelve degrees Fahrenheit, the same temperature is found 
at less than forty-eight feet; below this the ground becomes less cold, 
owing to the internal heat of the earth ; and toward three hundi'ed and 
ninety feet the sounding instruments finally arrive at layers of earth which 
are not frozen. 

Springs, like the soil, often show the average temperature of a country, 
owing to their source in the cavities of the rocks. Indeed, by placing a 
thermometer in the basins of springs, travelers can ascertain the average 
climate of the regions through which they pass. Observations of this 
kind are of great use, but they can not replace long and patient study of 
atmospheric heat, One spring is, on an average, colder than the surround- 
ing air, because its waters are produced by the melting of snows, or arise 
from rains that fell on the slopes of high mountains; another spring, 
slightly thermal, has traversed deep channels, where its temperature is 
raised by the telluric heat ; another has passed through fissures which are 
chilled or warmed by currents of air circulating in the caverns of the 

mountains. The slight 
alternations of heat and 
cold occurring in springs 
are analogous to those 
observed in the waters 
of rivers. Water-courses, 
always cooler in summer 
and warmer in winter, 
have a temperature all 
the more equal the great- 
er their velocity, because 
they are subject during 
less time to the changing atmospheric influences. Thus at Lyons, above 
the confluence of the two rivers, the fluctuations of temperature during 
various months of the year are seven degrees less in the furious Rhone 
than in the peaceful Saone. 

* Studei', Physikalische Geographic und Geologic^ t. ii. 



so» 


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Fig. 150. 



M:. A. Iff. J. J. A. s. o, :Br. J> J. 



Ordinary Temperatures of the Saone and the Ehone 
at Lyons. 



CONTRAST OF CLIMATES. 



335 



CHAPTER XXIII. 

CONTRAST BETWEEN THE CLIMATES OP THE NORTHERN AND SOUTHERN HEMI- 
SPHERES, BETWEEN THOSE OF THE EASTERN AND WESTERN SIDES OF CON- 
TINENTS, THOSE OP THE COASTS AND THE INTERIOR OP COUNTRIES, AND 
OP MOUNTAINS AND PLAINS. 

One of the most important climatic facts is that of the unequal distri- 
bution of heat in the two hemispheres. The observations made to the 
south of the equator during a long series of years are not sufficiently nu- 
merous for it to be possible to state a contrast of climate for each corre- 
sponding latitude of the two halves of the globe. But, taken as a whole, 
the northern and the southern hemispheres certainly differ in a remark- 
able way. This is proved by the immense size of the Antarctic ice-fields 
compared to the dimensions of those to the north, and the long distances 




Fig. 151. — Distribution of Temperatures in July. 

traversed by the flotillas of the former in their march toward the equa- 
tor.* The system of climates, like that of winds and currents, is drawn 
toward the north ; consequently the line of highest temperature which 
separates the two hemispheres is not identical with the equinoctial line, 
but is thrown more to the north ; indeed, the thermal equator of the 
earth passes through the Desert of Sahara toward the twentieth degree 
of north latitude. During the spring and autumn^ as well as during the 
summer of the northern hemisphere, the greatest heat makes itself felt 

* See p. 55. 



336 



THE ATMOSPHERE AND METEOBOLOOY. 



not only to the north of the equinoctial line, but also to the north of the 
twelfth degree of latitude,* It is only duri^ig the winter of Europe and 
Asia that the zone of greatest heat occupies fhe equatorial regions ; and 
even then it is to the north of the equator, in Africa, especially the 
mouths of the Niger, where the highest temperature is preserved. The 
disproportion which exists between the continental masses situated to the 
north of the thermal equator and those which stretch to the south is thus 
much less thaij it seems at first. 




Fig. 152. — Distribution of Temperatures in October. 

It is probable that the first cause of this climatic contrast between the 
continental and the maritime hemisphere is of an astronomical nature, 
and ought to be sought for in the difierence of relief presented by the 
two halves of the planetary orbit. The spring and summer of the north- 
ern regions are longer than the corresponding seasons of the southern 
countries. It is true that, during the warm season of the northern hemi- 
sphere, the earth is farther removed from the sun, and draws nearer to it 
during the period which is autumn and winter for Europe and Asia, A 
compensation may thei'efore be produced in the two hemispheres for the 
total quantity of,heat received; but in consequence of the inclination of 
the planet on its axis, it is also found that the number of hours of day- 
light is actually greater than that of the hours of the night to the north 
of the equator, while to the south it is the hours of the night which pre- 
dominate. It results from this that the northern countries receive more 
heat during the days than they lose by radiation in the nights, and that 
the inverse phenomenon obtains in the southern regions.f The real re- 
sult of all these contrasts between the two hemispheres is not yet clearly 
established, but it is not to be doubted that it constitutes a difference, 
* See Figs. 151, 152. t Adhemar, Lehon. 



DISTIUBUTION OF RAIN. 



3a: 



either periodical or permanent, between tke general climates of the two 
halves of the earth. According to Dove, the mean temperature would 
be 80° Fahrenheit at the tenth degree of north latitude, and only 78° at 
the corresponding south latitude ; at the twentieth degree the averages. 
would be, respectively, VV'o" and 74°; at the thirtieth and fortieth de- 
grees of the two hemispheres there would be still a slight diflerence to 
the advantage of the northern temperatures. According to Duperrey, 
there is a difference of about 1'8° in the mean tem^Derature of the two 
halves of the earth. 



aO 10 O 10 20 30 to Bo 60 TO 



90 IQO 1K> 




20 30 O 10 30 30 *0 50 CO 70 80 90 100 HO 



Fig. 153.— Distribution of Temperatures in January. 

Among the secondary causes which must result in rendering the cli- 
mate of the northern hemisphere a little warmer than that of the south- 
ern, we must reckon the distribution of rain. Considered in a general 
manner, the seas of the south are the area of evaporation, the continents 
of the north that of precipitation. When the water of the ocean is trans- 
formed into vapor, a great quantity of caloric becomes latent, and is borne 
away with the clouds, the particles of which it dilates ; with them it 
traverses the equator, and is carried away by the counter trade-winds ; 
then, when the latter sink on the temperate regions of Europe and North 
America, the clouds descend also, and are resolved into snow or rain, 
when all the latent heat from the Pacific or Indian OceauSj stored up iu 
the vapors, disengages itself and softens the temperature of the air, where 
it becomes free. Thus by the very fact of their existence, the continents 
of the northern hemisphere attract to themselves the heat and moisture 
necessary to the development of the animals and plants inhabiting them; 
but they also experience greater extremes of temperature than those of 
• the southern hemisphere, where the immense extent of ocean moderates 
the intense cold and great heat. 

22 



338 



THE ATMOSPHERE AND METEOROLOGY. 



If there is a contrast of temperature between the north and south of 
the worki, the opposition is not less marked between the east and west 
of continents. On the same latitude the coasts of California and Oregon 
enjoy a much milder climate than those of Japan, Mantchooria, and Ni- 
colajewsk; while in Western Europe the atmosphere is as temperate as 
that of the eastern coasts of North America, twenty degrees of latitude 
neai'er the equator. 

The cause's which thus soften the climate of the western shores in the 
two great continental masses of the north are due undoubtedly to the 
atmospheric and marine currents. The northern Atlantic and Pacific 
have each their Gulf Stream and winds from the south-west, and these 
two superposed currents constantly discharge their warmth on the shores 
washed by their waves. Eui'ope is especially favored in this respect. 
Not only is it warmed on the west by currents of water and counter- 
trade winds coming from the equator, but owing to the larger extent of 
water to the north of the continent, from the tropical seas having a great 
coast-line washed by the waves, it is less chilled by the polar winds than 
North America, whose seas are blocked by snowy islands. While Lab- 
i-ador and Hudson's Bay Territory have a soil that is frozen to a great 
depth, Northern Europe projects its islands and peninsulas into water 
incessantly renewed by the tepid currents from the south, and its inland 
seas open like so many reservoirs, to maintain to the centre of the conti- 
nent a temperature equal to that of the outer shores. Nor is this all ; 
immediately to the south of Mauritania extends the immense furnace of 
the Sahara, which warms by its winds the countries of Europe and West- 
ern Asia. Thus, in respect of climate, Europe enjoys a special privilege. 

The north, the west, and the south all 
aid in the task of raising the mean 
temperature, and during summer all 
the surrounding seas store up heat, to 
exhale it gradually during the winter. 
The east, however, sometimes sends 
1e its dry winds, very hot in summer, 
and intensely cold in winter ; but the 
Scandinavian mountains, the Sudetes, 
the Carpathians, and the Alps, rise 
like barriers across the path of these 
winds, and shelter Western Europe. 
We may form an idea of the influence 

Fig.lS4.-Variatiou of the Temperature at Paris of the wiuds On the climatCS of France 
during the prevalence of different Wiuds (after and England by the accompanying fig- 

Mahimann and Laianue). ^^,^ . ^^^.^^ occasionally the north-east 

winds raise the summer temperature of Paris, and depress that of winter 
almost to freezing-point, the winds from the south-west equalize the cli- 
mate, bringing freshness during the warm season and heat during the cold. 
Another great climatic contrast is that presented by the sea-shore, and 




CLIMATE OF EUROPE. 



339 



the regions sitiiated in the interior of continents under the same latitude. « 
In consequence of the incessant mingling of its waters, the sea equalizes 
temperatures; into the polar regions it pours the warm waters /rom the 
equator, under the tropics it receives the afflux of the polar currents, the 
revolution of its waves bringing coolness to the burning zones, and carry- 
ing warratli to the region of snows. Owing to its mobility, the sea has, so 
to speak, no degrees of latitude ; it mixes climates, diminishes the extremes 
of heat and cold on the shores which it bathes, maintains in the march of 
the seasons a pace much more gently graduated than it is in countries re- 
mote from the ocean. To countries which would be subject to polar cold 
if they were not situated on the border of the waves, the sea imparts the 
warmth of the temperate zone ; it prolongs spring into summer and au- 
tumn into winter. The intense cold and overwhelming heat to which one 
is subjected in the interior of continents are completely unknown in the 
open sea; no traveler has yet observed any oceanic temperature above 
eighty-eight degrees.* We may judge of the moderating influence of the 
sea by the comparison of two cities situated nearly in the same latitude, 
one in the interior of the continent, and the other on the shores of the 



























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3715 3955 9?02 12°73 TijeS 16?67 16?50 lt»32 



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PtymoaQiBoTzzlfN. 

Wia-Sa'W^Sz^lSl^N. ,5?*0 3?tb 0?!tS e°Oe 12?52 16?05 18?22 U?83 13°35 2?2f; V.Jh 2° 

Jfta'? Feb"^ March Aprfl ]May June July Aii°t Sept'7' Oct? NoVT Dp**? 
Fig. 155.— Continental Climate of Warsaw, and Oceanic Climate of Plymouth. 

ocean, such as Plymouth, bathed by the mild vapors of the Channel, and 
Warsaw, placed nearly in the centre of the continent of Eui'ope. M, 
P^mmanuel Liais, who has deeply studied this question, has taken as an 
example two places muchi nearer to one another — Paris and Cherbourg. 
Though this latter town is nearly one degree of latitude more to the north 
than Paris, its mean temperature is, notwithstanding, higher: it is 52*3°, 
that of Paris being only- 51-3°. The difference is much greater between 
the winter climates of the two cities, for during a series of nine years the 
mean temperature of the three winter months was 44° at Cherbourg, and 
38° at Paris. The contrast between the winter temperature of the two 
localities Is all the stronger the intenser the cold at Paris, for it is precise- 
ly then that the relatively warm waters of the sea exercise their greatest 
influence in softening the climate on the coast. On the other hand, the 
sea lowers the temperature of Cherbourg, for in summer the warmest 

* Kamtz, Meteorologie. 



340 THE ATMOSPHERE AND METEOROLOGY. 

I, month is cooler by 2 '6° than Paris. In short, the six months from Octo- 
ber to March are warmer, while the six months from April to September 
are coole^r. The greatest difference between the highest and lowest annu- 
al temperature was 78° at Paris during the four years which elapsed from 
1848 to 1852; at Cherbourg it was only 66° during the same period. 
This difference between the climates of the coasts of Cotentin and the 
valley of the Seine produces a corresponding difference between the vege- 
tation of the two districts. In the environs of Cherbourg, fig-trees, lau- 
rels, myrtles, and a great number of other species of trees and shrubs, 
which would perish in the neighborhood of Paris, are very luxuriant. It 
is the same on all the coasts of Brittany, and especially at Roscoff, where 
an enormous fig-tree is to be seen, one of the most magnificent of the 
wonders of the vegetable world. 

The contrast is greater still between islands surrounded by a compara- 
tively warm sea like Ireland and Great Britain and the regions entirely 
continental, situated, like the steppes of Tartary or the plateaux of Cen- 
tral Asia, at more than six hundred miles from the shores of the ocean. 
While in Ireland, which is bathed by the waters of the Gulf Stream, a 
temperature comparatively 900I in summer and w^arm in winter preserves 
a constant vegetation, transforming it into the " emerald isle of the seas ;" 
the steppes of the Bashkirs, lying under the same latitude, are by turns 
burned up by the heat and frozen by the cold ; and all vegetation there is 
impoverished. In the environs of Astrakhan, which is at the same dis- 
tance from the equator as the vineyards of the Charente, the grapes yield 
excellent wine, owing to the gi'eat heat of summer, but have to be buried 
in winter, to escape the fatal action of the cold. 

The other climatic contrasts observed in different countries at the same 
latitude result from the variety of surface and soil. High mountains 
change the normal temperature of a country either by arresting or turn- 
ing aside warm or cold winds, or by lowering the temperature of the at- 
mosphere and depriving it of the moisture wlftch it contained. Forests 
have also their action. The}'- shelter the ground against the rays of the 
sun, and when the heat received by the earth returns into space, their in- 
terlacing branches are an immense obstacle to radiation. The general in- 
fluence which they exercise oh climate is moderating just as that of the 
sea: they assimilate extremes by cooling the summer and warming the 
winter, in the same way that a moist and marshy soil receives heat more 
slowly than arid lands or sandy tracts, but also retains it with more te- 
nacity. Each exterior feature of the planet modifies the local climate, 
and distinguishes it from that of every surrounding district in its diurnal, 
monthly, annual, and secular oscillations. 



V 



The Ocean,(&c 



I S T H E R ^ 




l'jngr?ljy Riiiard. 



HARPEP.&. BRC 



LINES. 



PL„\VI 




-S NEW YORK 



ISOTHERMAL LINES. 341 



CHAPTER XXIV. 

leOTHEEMAL LINES. — THERMAL EQUATOR. — POLES OP COLD. — INCREASE OF 
TEMPERATURE TOWARD THE POLES. — OPEN SEAS. 

Fifty years ago Humboldt first conceived the idea of uniting by lines 
all parts of the earth having the same annual average temperature. These 
imaginary lines, traced on the circumference of the globe, are called i$o- 
thermals; they give the thermal latitude, which differs widely from the ge- 
ometrical latitude. While the lines of degrees traced every sixty-nine and. 
a half miles parallel to the equator are of a perfect regularity, and cor- 
respond to other imaginary lines traced by astronomers oh the skies, the 
isotherraals are contorted in numerous sinuosities of different forms in all 
l^arts of the earth. The various causes which modify the temperature of 
a place, and consequently curve the isothermal lines toward the pole or 
the equator, have been enumerated with the greatest care by Humboldt. 
Next to latitude, the principal causes known* are the direction of the at- 
mospheric and marine currents, the elevation above the sea-level, the ar- 
rangement of mountain chains, the outline of the coasts, their relation to 
the neighboring seas, the nature of the soil and vegetation. 

The thermal equator — that is to say, the curve of the greatest average 
heat on each side of which the temperature gradually diminishes toward 
the poles — lies almost entirely in the northern hemisphere, which is warm- 
er than the southern. According to the observations of meteorologists, 
this line traverses America near th^ isthmus of Panama at the point of 
junction of the two continents, then runs along the coasts of Colombia, 
Venezuela, and Guiana, to the embouchure of the Amazons, and there 
bends slightly to the south of the equator. Over the Atlantic the curve 
of the greatest heat ascends obliquely toward the African continent and 
the Sahara, the hottest region of the whole world. The precise direction 
taken by the thermal equator is not yet known either in this burning 
country or in the Arabian desert, or ove'r the coasts of the Indian penin- 
sula : it is only certain that in traversing the Old World it continues to 
keep north of the equinoctial line. In the Sea of Sunda and the Pacific 
Ocean it bends again to the south, ajid perhaps penetrates into the south- 
ern hemisphere at various points. Seeing the want of continuous thermo- 
metrical observations over a long period of time, the thermal equator can 
only as yet be traced on the maps in a provisional manner : it is simply 
an approximation that subsequent researches will bring nearer and nearer 
to the ti'uth. 

Over vai-ious points of this line of. greatest heat the temperature is far 
from being the same everywhere. Above the ocean it is from 77° to 79°; 

* See above, p. 331. 



342 THE A T3I0SPHERE AND METEOR OLOGT. 

on the coasts of Colombia and Guiana it is 81° on an average; at Calcut- 
ta it attains 82'5° ; at the mouths of the Niger it is much greater (85'3°), 
and undoubtedly in many parts of the interior of Africa and Arabia never 
reached by refreshing breezes from the sea, the mean temperature of the 
year is still higher. Thus the tracts where this exceptional heat prevails 
form on the course of the thermal equator a sort of island, the outlines of 
which wander according to the diiferences of relief on the surface and the 
atmospheric phenomena. The researches of Mahlmann have proved that 
islands of less heat exist in the tropical zone, and that the thermal equa- 
tor sometimes bifurcates and incloses colder regions. 

The sinuosities of the isothermals, properly so called, are caused over 
all the terrestrial circumference by these isothermal islands of a higher or 
lower temperature. In the southern hemisphere, where the continents are 
diminished gradually toward the south, and where the moderating influ- 
ence of the ocean tends to eliminate all climatic difierences, the lines of 
equal annual temperature seem to be pretty regular, and in the Antarctic 
Ocean they may be considered jDarallel to the degrees of latitude. The 
most marked curves of these isothermals of the south are those which are 
developed immediately to the West of Africa and South America, under 
the influence of the currents of cold water which flow toward the equator 
along the coasts of these two continents. 

In the northern hemisphere the sinuosities of the isothermal lines are 
much more marked than those in the southern, and cut the degrees of lat- 
itude at all angles. Considered in a general manner, the isothermal lines 
of the northern hemisphere have the form of a double wave, the crests of 
which rise above the western shores of Europe and toward those of Cali- 
fornia, while the depressions coincide with the eastern coasts of the Old 
and New World.* The highest isothermal wave is that which rises oflT 
the coast of New England, Newfoundland, and Ireland, the culminating 
point of which is found to the north of the British Islands; one would say 
that it was traced over the Gulf Stream, and in fact it is this current of 
.warm water which drives the whole system of isotherms toward the north. 
The line of 59° Fahrenheit which passes over the coast of North Carolina 
near Cape Hatteras, cuts the south of France from Bayonne to Montpel- 
lier at nine degrees latitude farther to the north. Between New York 
and Dublin, where the mean temperature is the same (50°), the difference 
of latitude is 13°, it is 16°, or nearly 1100 miles, between Quebec and 
Trondhjem, where the isotherm of 39-2° passes. And the difierence is 
still greater for the line of freezing-point. 

Whatever may be the sinuosities of the lines of equal temperature, they 
all indicate a more or less rapid decrease of heat between the equator and 
the two polar zones. In the northern hemisphere it has been possible to 
trace approximately the various isothermal lines as far as that which gives 
an average temperature of five degrees, but beyond this observations have 
been too rare for it to be possible to mark lines the course of which is not 

* See p. 76, 



Tke Ocean, <fcc. 



SOTHERMAL 




IngtELved by Erhard 



iiAi^^PER i'. BR 



S OF THE PACIFIC 



ri. XMI 



V' A 1- c t i c_^>| ^:, ^ - C i ,r c 1 o 



60 




LrawTi bv AVuillcniin alter Cli. Wilkes 



P.S Ni.V/ YORK 



INCREASED WARMTH AT THE POLES. 343 

alniost entirely hypothetical ; the general direction, however, of the curves 
renders it very probable that in the polar circle there exist at least two 
isothermal islands of cold corresponding to the two isothermal islands of 
heat which are found in the neighborliood of the equator. According to 
Brewster, there are in the frozen ocean of the north two of these regions 
of greatest cold, real meteorological poles, moving incessantly according 
to the alternations of the seasons, but in all their oscillations keeping 
themselves at several lunidred mi'les distant from the geometrical pole. 
One of these poles of cold is found to the north of the Asiatic continent, 
not far from the archipelago, known under the name of New Siberia, and 
its average temperature is about 1*5°. The American pole oscillates in 
the midst of the western islands of the polar archipelago, and the average 
there is more than two below zero. The researches of Miihry have ren- 
dered it very probable that in the Antarctic hemisphere there also exist 
two poles of cold.* The regions whose climate is most severe would thus 
be situated under latitudes which man has already visited, and conse- 
quently the poles properly so called would not be that formidable citadel 
of ice that geographers once imagined. It is erroneous to believe in the 
existence of an ice-field all round the pole gradually thickening toward 
the centre, and erroneous to picture to one's self the two extremities of 
the terrestrial axis as forever inapproachable because of the intensity of 
the cold. 

Besides, the calculations of the mathematician Plana tend to make us 
believe that the total quantity of heat 4-eceived increases gradually from 
the polar circle to the central depression of the Arctic zone. According 
to the researches made a long time since by the mathematician Lambert, 
it was thought that, the total insolation at the equator being taken as 700, 
it would be no more than 646 at the Tropic of Cancer, 516 at the 45° of lat- 
itude, 350 at the Arctic Circle, and that at the pole itself it would be rep- 
resented by the much lower number of 287. In consequence of elements 
neglected in these calculations, it is found, on the contrary, that the mean 
temperature, after having gradually decreased from the tropics to the lim- 
its of the glacial zone, afterward rises in a normal manner as far as the 
pole, which would thus be, at least theoretically, the waripest point of all 
the polar region, the cold being less severe at the North Pole than it is 
on the coast of North America and Siberia at 1600 miles farther to the 
south. However it may be, it is certain that during the six months of 
summer the insolation is greater at the pole than at any other part of the 
■ Arctic zone, for, according to the expression of M. Gustavo Lambert, "it 
is always noon" during the summer of the pole because of the position of 
the earth relatively to the sun. According to calculations made by Hal- 
ley nearly two centuries ago, the summer mean must increase from the 
60° of latitude to the North Pole in the proportion of nine to ten. 

The experience of polar navigators has fully confirmed the results of 
the theory, according to which the series of Arctic isothermals would 
* Zeitschrift filr Meteorologie von Jelinek, 18(57. 



344 THE ATMOSPHERE AND METEOROLOGY. 

mark a gradual increase of temperature. On his celebrated voyage of 
1827, Parry ventured with his bold companions on the great ice-field 
which extended to the north of Spitzbergen. Imagining that this field 
was a real continent of ice, he hastened to cross these polar regions as if 
they were the frozen steppes of Siberia ; but as the sledges advanced to- 
ward the north, the ice-field became lighter and more fissured. It was 
floating to the south, carried along by a drifting current ; and before the 
travelers, on the side next the pole they so much desired to ajDproach, 
stretched an open sea where floated only a few scattered pieces of ice. 
At the extreme point of his perilous expedition toward the north, Kane 
also discovered an immense sheet of water completely free from ice, and 
that immediately to the north of Smith's Strait, where the mingled frag- 
ments of glaciers and ice-fields form a labyrinth diflicult to traverse. To 
the north of the coasts of Siberia, all incumbered with " toroses," Wran- 
gell and other navigators have also ascertained the existence of an open 
■sea, to which they have given the name of Polynia. Finally, in the Ant- 
arctic hemisphere, Sir James Ross found tracts relatively free from ice be- 
yond that high wall through which he had to make his way with so much 
difficulty. Thus it may be admitted as probable that there does not exist 
a region of unbroken ice at the two extremities of the earth, but rather 
an open sea, with a relatively elevated temperature, and surrounded on 
all sides either by islands and archipelagoes, or by a circular ice-field. 
The two girdles of northern and southern ice would be, as M. Charles 
Grad says, the visible representation of the isothermal lines of the lowest 
temperature, and on each side the severity of the cold would diminish. 



EXTREMES OF TEJirPERATUME. 345 



CHAPTER XXV. 

EXTEEMES OF TEMPEKATURE. — ISOCHIMENAL AND ISOTHERAL LINES. — 
DAILY AND MONTHLY VARIATIONS. DECREASE OF WARMTH IN THE UP- 
PER STRATA OF THE AIR. VARIATIONS OF CLIMATE DURING THE HIS- 
TORICAL PERIOD. 

The total difference observed on various points of the earth between 
the highest and lowest extremes of temperature much exceeds 300 de- 
grees. Captain Back endured at Fort Reliance, in English America, 70° 
below zero, which is hardly inferior to that which is believed to prevail 
in the interplanetary spaces ; a Russian traveler observed near Semipala- 
tinsk 72 degrees ; still more, Gmelin is said to have experienced (?) at 
Kiringa, in Siberia, the truly terrible cold of 121° below zero;* while 
M. Duveyrier, traveling in the country of the Touaregs, saw the thermo- 
metric column indicate a warmth of 155*5°. Thus, without taking into ac- 
count the observation, probably erroneous, the series of ascertained temper- 
atures includes from 250 to 260 degrees, and man has certainly to endure 
frequently extremes of cold and warmth, without being able to measure 
them, still greater than those which have been regularly observed. Even 
on one point of the earth the highest and lowest temperatures in the course 
of the year often present the enormous difference of more than 144 degrees. 
In the vast frozen plains of North America, where Back had to endure the 
severe cold of 70° below zero, Franklin experienced during the long sum- 
mer day a torrid heat of 87°. Between these two extremes, the scale of 
temperature traversed in the year is about 157 degrees. Not far from the 
equator, the so-called " burning " regions of the Sahara present, according 
to Duveyrier, a thermometrical difference almost ^ considerable as that 
of the polar countries of New England. f This is because, in spite of the. 
difference of latitude, the deserts of Africa and the granitic plains of North 
America resemble each other by their continental position, and the rela- 
tive uniformity of their relief Remote from the ocean, that great equal- 
izer of climate, and destitute of high mountain chains, which could arrest 
the cold or warm winds blowing from different points of the horizon, these 
countries must be subject to very abrupt alternations of temperature. 
How much more equable are climates where the moderating miction of 
marine waters, as at Surinam, the Canaries, and Madeira, or else the shel- 
ter offered by a rampart of mountains, as on the coast of the Genoese 
Alps, maintain a temperature whose extremes only differ from 20° to 55°. 
In France, a country which represents a fair average through a great many 
of its physical features, the difference between the intensest cold and great- 

* Thomson ; Sir John Herschel, Physical Geography, p. 238. 
t See The Earth, the section entitled Plains. 



346 THE ATMOSPHERE AND METEOROLOGY. 

est heat rarely reaches 99°, and in ordinary years does not exceed 81°. 
During all the series of meteorological observations made at Paris during 
the last century, the mercury has oscillated, in all, 110'5°; at Nice the 
greatest variation has been 78°. 

Through this greater or less change in the height of the thermometer 
in various countries of the world, it results that the lines of equal temper- 
ature for each season, and more still for each month, are much more sinu- 
ous than the isothermals of the year. The name of isochimenal lines is 
given to those which unite all the localities where the winter temperature 
oscillates to about the same extent; the isotheral lines are the curves drawn 
through those places which present on an average the same summer tem- 
perature. We can also cover maps with isoeral lines, or equal tempera- 
ture in spring, and isometoporal lines, or equal temperature in autumn, 
and isome7ial lines, or curves of average heat for each month in the year, 
might even be drawn across the continents and seas. But meteorological 
observations not being yet numerous enough for this immense labor to 
oifer all the certainty desired, it is better to limit one's self provisionally 
to the study of isotheral and isochimenal lines, which have, above all 
other lines of seasonal or monthly temperature, the advantage of indi- 
cating the extreme periods in tlie alternations of heat. 

The direction followed by the isotheral and isochimenal lines in Europe 
and IsTorth America is a singularly striking example of the influence 
which the unequal distribution of land and sea exercises on climate. In 
summer, when the northern hemisphere is inclined toward the sun, and 
receives the greatest quantity of heat, the countries situated in the inte- 
rior of the continents of the north are much more heated than those bor- 
dering on the sea. During the cold season the contrary takes place : the 
winds and the currents coming from the equatorial zone temper the sever- 
ity of the cold in the neighborhood of the coasts, while far into the conti- 
nents the tempering influence of the ocean and the aerial currents of the 
south make themselves much less felt. Consequently, the isotheral lines 
curve toward the north in the two northern masses of the Old and New 
World, and bend to the south, in traversing the Atlantic and the Pacific ; 
on the other hand, the isochimenal lines bend to the south, in their passage 
across the continents of America, Europe, and Asia, and curve in certain 
places by more than 600 miles to the north, in crossing the sea. The con- 
trast between the curves of the continental climate and those of the ocean- 
ic becomes still more striking when we take, in order to oppose them to 
one another, as Kiepert did, the isothermal lines of January, which is, on 
an average, the coldest month, and those of July, which is the warmest. 
In Great Britain especially, this opposition of winter and summer climates 
is remarkable. The mild influence of the Gulf Stream and the west winds 
goes even so far (as is shown by one-half of Fig. 156) as completely to 
lead back the isochimenal lines, which are thus developed from the south 
to north, instead of running from west to east parallel to the degrees of 
latitude. 



Tlio Occiiii.cVc. ^ PL .Win. 

ISOTHERMAL LINES OF JANUARY & JULY fN THE NORTHERN HEMISPHERE. 



K 



90 



80 



70 



60 










r>,\:\Mi In \.\uillfT>"VU> 



•lo-fraved by Evhavd. 



VNGERTAIN SPACES OF EQUAL TEMPERATURE. 



347 



Isochimcual Lines. 



Isotheral Linos. 



I S" 




Fig. 156 Climate of the British Isles. 

We can understand the decided influence which these inequalities, with 
their alternations of warmth in countries having in other respects the 
same mean temperature, must exercise on plants and animals. One kind, 
which can well support the severity of winter without dreading the heats 
of summer, is propagated over vast regions in the interior of continents ; 
another kind, which shrinks from the low winter temperatures, when re- 
mote from the sea-shore, does not pass latitudes which it crosses by sever- 
al degrees in the neighborhood of the ocean. Thus the elk lives in the pe- 
ninsula of Scandinavia, which is bathed by the tepid Avaters of the Gulf 
Stream at 700 miles farther north than in Siberia, with its extremes of 
heat and cold.* 

The course of the various isothermal lines depends in great part simply 
on probabilities, since between all the points whose temperature has been 
observed during a longer or shorter period of years, or only months, there 
remain here and there wide intervals where no thermometrical notes have 
yet been made. There are uncertain spaces through which meteorologists 
can not draw lines of equal temperature, inasmuch as they have no series 
of precise observations on which to base them. Thousands of persons in 
the United States, Canada, the Antilles, Hindoostan, and South Africa 
have joined their eflbrts to those of all the ofticial savants, to note down 
the innumerable oscillations of heat- and cold which, by their grouping, 
* See the two folio wins; books. 



348 



THE ATMOSPHERE AND METEOROLOGY. 



may reveal the laws of temperature. Day after day they ascertain the 
horary variations which afterward allow them to establish the mean heat 
of the day, month, and year, and then to compare the place whose condi- 
tion they have studied with other localities where the alternations of heat 
and cold succeed each other in a more or less analogous manner. 

From millions of horary variations which have been observed for a cen- 
tury in various parts of the world, it results that the greatest heat of the 
day makes itself felt, on an average, between one and two o'clock in the 
afternoon, while the lowest temperature precedes sunrise by an hour, or 
even half an hour. It is easy to understand why the extremes of heat and^ 
cold do not coincide exactly with midday and midnight. After midday 
hour, when the sun again begins to incline toward the horizon, its rays 
continue to heat the ground and the atmosphere ; it is only later that the 
loss of warmth caused by i-adiation equals, and then exceeds, what is 
gained, and the temperature begins to sink. During the night the con- 
trary phenomena occur; the earth and the atmosj^here which surrounds 
grow colder, till dawn announces the near appearance of the sun, and the 
nocturnal radiation is compensated for by the increasing heat of the new 
day. In the island of Java the diurnal heat attains its maximum a few 
minutes after one o'clock in the afternoon, and is, on an average, found at 
its minimum a little before six o'clock in the morning. At Paris, accord- 
ing to the observations of Bouvard, the highest temperature (58°) makes 
itself felt at two o'clock in the afternoon, the lowest (45°) falls at four 
o'clock in the morning, and the mean heat of the day, which is at the 
same time that of the year (51 '2°), returns at the corresponding periods 
of 8.20 in the morninac and the same hour in the evening. 



o 


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hi 




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a 


oc5 


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— , . . 1 . ; . — ■ — ; ■ _i_-.— ' ; ■ ; ; ; 1 r- -— u- — : : ' '■ ! 




















































7> ; : ; 1 1 , > ; . : ■ ; : : i ■ , '. ■ . . ; ' : : • 










ro I : 1 ; ; ■ :..;,; , ■ ; ; : : : ■ :■,;;.,: 



2 3 & 5 G 7 6 6^9 10 U Noon 1 2 3 ft 5 6 7 8 8^9 10 11 

Pig. 157.— Diurnal Variations in the Mean Temperature at Paris. 

The monthly variations present in their regular oscillations the same 
phenomena as the hourly ones. It is not at the solstice of June that the 
northern hemisphere enjoys the greatest quantity of heat, and it is not at 
the solstice of December that it is subject to the severest cold. After the 
sun has ceased to illuminate from the zenith countries situated beneath 
the Tropic of Cancer, the heat still augments till July, and even till Au- 
gust, in a great many regions situated toward the north pole, and in 
mountainous countries. On the other hand, the greatest cold of the north- 
ern hemisphere continues, and is even aggravated, when the solar rays al- 
ready bring an increasing quantity of heat. In Europe and North Amer- 



MONTHLY VARIATIONS OF TEMPERATURE. 



349 



ica it is the month of January that is ordinarily the coldest; and there are 
even some towns, like Palermo, Gibraltar, and New Orleans, where the 
lowest temperature of the year falls in February, hardly a month before 
the vernal equinox. 

In the neighborhood of the equator, illuminated by a vertical sun, the 
monthly variations of temperature are much less important than in coun- 
tries situated beyond the tropics, and they depend much more on the di- 
rection- of the winds and the alternation of rains and droughts, than on the 
position of the sun in the ecliptic. Thus at Singapore the total difference 
between the coldest and hottest month is scarcely 3 '5°. To the south of 
the equinoctial line the monthly variations become more and more con- 
siderable, but in the reverse order to that ascertained in the northern hem- 
isphere. It results from the researches of Dove that, taking the average 
of all the temperatures over the whole world, the month of July is the 
hottest of all the year. 



Jan^FebTy^arch April May June Juty A^|^ Sept? OcgrNov^P&fc 



Hio Janeiro Ss'H.^S ,_. 

Madras m'^^'^^f.l-. 
Cape 33°« S. 



Mesjsina ae^llt. 
iVice 43°4olSL. 
Paris 4ePa2JV_. 



BootZuaFeZix 70°1K. :, 



Yhkutak QsOUL 




Fig. 158.— Monthly Variations of the Temperature in various Places. 

In order to account for the average variation of cold and heat from 
month to month, and at different hours of the day, meteorologists have 
had the ingenious- notion of drawing curves which, by their deviation 
from the central point taken as zero, indicate the hourly temperature for 
every month of the year. We give as example of these diagrams a fig- 
ure which enables one to read the temperature of various hours at Brus- 
sels during all the cycle of a year. Another very elegant figure (Fig. 



350 



THE ATMOSPHERE AND METEOROLOGY. 




Pig. 159.— Temperatures of the same Hours in different Months, at Brussels (after Qu^telet). 

160), drawn by M. Leon Salanne, after the data of Kamtz, represents the 
thermometrical curves at all hours of the day according to the month : it 
is the meeting-point of the horizontal and vertical lines which indicates 
the degree of heat. Thus, as is seen by Figure 161, constructed with the 
same elements, the difference of temperature between day and night is 




JUacn iyr. May June Jid. Aurf. Sept. Oct. TTovr Dec Jan, reb.llai; 
Fig. 160.— Variation of tlie mean monthly Temperature, in the same Hours, at Halle. 



REVERSAL OF CLIMATIC ORDER. 



351 



much greater in summer than in winter. Besides, the curves show clearly 
that the long summer is followed by a short one, called "St. Martin's 
summer," and that a return of cold is generally felt in May. 




Fig. 161— Temperature of the djflfereut Hours at Halle. 

Above the surface of the ground meteorologists observe in the atmos- 
pheric strata a decrease of tempei'ature similar to that which takes place 
between the torrid and the frigid zone. The rarefied air of the upper re- 
gions must necessarily be chilled the nearer it approaches to the cold in- 
terplanetary spaces, and loses the watery vapor which serves as a screen 
for the nocturnal radiation of heat. Nevertheless, it is seldom that the 
temperature falls in a perfectly regular manner from the surface of the 
ground and the ocean to the heights of the atmosphere ; for winds, clouds, 
and other meteoric phenomena incessantly modify the condition of the 
aerial strata, and frequently those which rise on the sides of a mountain 
penetrate from a relatively cold zone to a more elevated temperature. 
The order of the climates is found reversed. Thus, in the winter from 
1838-1839, the cold was 4° below zero at Andancette, on the banks of 
the Rhone ; while in the mountains of St. Agr^ve, at 3690 feet higher, 
it was 10*4° above zero. In the same way Mr. Glaisher ascertained, in 
the night of October 2, 1867, a continuous increase of warmth to the 
height of nine hundred and eighty-four feet. In other ascents, the same' 
aeronaut had found no appreciable change between the temperature of 
the ground and that of the atmosphere to the height of 2300 feet.* Be- 
sides, M. Prestel has proved, by long and precise observations, that in 
that portion of the air which rests immediately on the ground the heat 
increases constantly from below to at least thirty feet.f In consequence 
of meteorological perturbations, this zone of increasing temperature may 
sometimes rise to a considerable height above the surface. 

Unfortunately the series of regular observations made at a great height 
are still very rare ; and even in Switzerland, where so many eminent men 

* Kamtz and Martins, Meteorologie, p. 200; Marie Davy, Les Mouvement de l' Atmosphere, 
f. 104. 

t Zeitschrift fiir Meteorologie von Jelinek, January 1, 1867. 



352 



THE ATMOSPHERE AND METEOROLOGY. 



busy themselves in scientific researches, there only exist two points above 
2000 feet — the hospice of St. Bernard and the pass of St. Gothard — where 
the monthly averages of temperature are ascertained with certainty. It 
is therefore only in an approximate manner that we have been able to cal- 
culate the laws according to which the heat diminishes in the higher stra- 
ta of the air during the various seasons. At ail events, it is certain that 
during the summer and in full sunlight the aerial strata of difierent tem- 
perature are much thinner in pi'oportion than in winter and during the 
night. One could say in a general way, with Helmholz, that on the sides 
of the Swiss mountains the heat diminishes upward by one degree at in- 
tervals of three hundred feet in summer and four hundred and fifty feet 
in winter ; according to M. Charles Martius, the average intervals for the 
entire year would be from three hundred and twelve to three hundred and 




Fig. 162.— Succession of Climates on the Slopes of Moat Blanc. 



fifteen feet. Other savants have found slightly difierent figures. Thus 
De Saussure, to whom the honor belongs of having first made observations 
of this kind, ascertained that on the western slopes of Mont Blanc the de- 
crease of temperature during the warm season was about one degree for 
three hundred feet. However, each mountain diflers in this respect, and 
on isolated peaks like Le Ventoux the superimposed climates are much 
closer to each other than on the sides of heights whichform part of vast 
mountain systems. 

Studer estimates the average height of the isothermal line of fifty de- 
grees in the Alpine masses at 1300 feet high; the line of forty-one de- 
grees would rest at 4200 fe'et above the sea-level ; that of thirty-two de- 
grees would surround the mountains at 7200 feet, and the temperature 
would continue thus to diminish. one degree for every three hundred feet 
to the summits. Thus, in the maps which represent the relief of the 
mountains by concentric curves of level, these curves may serve to illus- 



PROBABLE CLIMATAL CHANGES. 353 

trate not only the increase of altitude, but at the same time the fall of 
the average temperature ; they are like superimposed degrees of latitude. 
Further, the observations of aeronauts have rendered it probable that in 
the upper regions of the atmosphere the interval increases more and more 
for every decrease of one degree in temperature. Beyond the limits of 
the atmosphere all the heat which the rays of the sun impart to the earth 
disappears in the cold of space, which is estimated at about one hundred 
and eight degrees below the freezing-point, and reigns supreme through- 
out interstellar space. 

The study of the climates which now prevail on the surface of the globe 
ought to be completed by that of the changes experienced during histor- 
ical times; unfortunately, the earliest meteorological observations date 
from an epoch so recent, and the too scanty and very uncertain facts on 
which we have to depend to arrive at a knowledge of the condition of the 
temperature in former centuries do not authorize us to establish a precise 
law of the modification of climates. Long ago Ai'^go attempted to es- 
tablish, by very ingenious considerations, that in the space of the last 
thirty centuries Palestine has continually enjoyed a temperature from 
seventy to seventy-one degrees ; for now, as in the times of Jewish his- 
tory, the northern limit of the zone where dates ripen and the southern 
limit of the vine coincide, on the banks of the Jordan,* Nevertheless, 
Arago did not refuse to believe that in Western Europe the laws regula- 
ting the temperature have notably altered ; this is proved, he says, by the 
gradual retrogradation of the vineyards toward the south. In our days 
the vine is no longer cultivated on the shores of the Bristol Channel, nor 
in Flanders, nor in Brittany; and in these countries, which the chroniclers 
— perhaps too laudatory — tell us produced exquisite wines, grapes can 
not ripen now save in exceptional years. Mr. Fuster says that titles of 
property going back as far as 1561 state that formerly the vintage took 
place at heights of 2000 feet on the sides of the mountains of Vivarais, 
where in the present century the vine no longer bears fruit. In the same 
way, in the environs of Carcassonne, the culture of the olive-tree has retro- 
graded from nine to ten miles to the south in a hundred years ;f the sugar- 
cane has disappeared from Provence, where it was acclimatized; the or- 
ange-trees of Hyeres, the cultivation of which extended in the sixteenth 
century as far as the village of Cuers, have been struck with disease un- 
der a sky that is no longer favorable to them, and have been obliged to 
be replaced by trees with less delicate fruit, such as peach or almond 
trees. Ought we to see, with M. Alphonse de Candolle, in this gradual 
retreat of the vines, olives, and orange-trees, only a simple economical fact 
resulting from the greater facilities for commerce, or is it indeed allow- 
able to infer from these facts that the annual temperature, or at least the 
summer heat, has diminished in France since the Middle Ages ? It seems 
impossible to reply with certainty. 

* Annates des Longitudes, 1834-. 

t Bourlot, Variations de Latitude et de Climat, p. 46. 
23 



354 THE ATMOSPHERE AND METEOROLOGY. 

It is known also that in many parts of the Alps tradition speaks of a 
continuous refrigeration of the mountains.* According to all the bota- 
nists who have traveled in the Alps of Savoy and Switzerland, and the 
Carpathians, the limits of the high pine forests have sunk sensibly on the 
slopes of the mountains. M. Kerner estimates the retreat of the forest 
vegetation at over 300 feet in vertical elevation during the last two or 
three centuries ; everywhere are perceived, beyond the present limits of 
the greater vegetation, the remains of dried-up trunks and half-decayed 
fragments of immense roots. Perhaps mankind and the animals which 
accompany them to the high pasture-grounds — cows, sheep, and especial- 
ly goats — are the true authors of this gradual decline of the limit of trees. 
In the course of centuries the forest has, little by little, ascended the es- 
carpments and the slopes, the higher trees protecting the smaller ones 
from the cold with their branches ; but if the least attack be made on 
this battle-front either by the axe of man or by the teeth of animals, 
wind, snow, and avalanches instantly profit by the gap, and the forest be- 
gins to descend on the slopes of the mountains. Some botanists attrib- 
ute this retreat of the pine forests not to the diminution of the annual 
heat, but to the great inequality of the temperature, to the moi-e sudden 
alternations of cold and heat, to the frosts and thaws of the spring. 
What renders this hypothesis very probable is, that in the plains of Hun- 
gary constant encroachments of the plants of the steppes have been ob- 
served in a westerly direction, and yet no movement in the contrary way 
has been remarked of western species. It is concluded from this that the 
excessive climates advance gradually toward the west.f 

Besides this, direct thermometric observations have proved that for a 
century the cold has slightly increased at various places in Germany — at 
Ratisbon, Prague, Hamburg, and Arnstadt ; the month of December hav- 
ing become relatively much colder, while January has become notably 
warmer.| On the other hand, Glaisher has ascertained that the mean 
temperature of England has increased by two degrees in the last hundred 
years, and for the single month of January the increase of temperature is 
no less than three degrees. In France the extremes have drawn nearer 
to each other, the climate having become milder and more equable. 

Another climatic change seems likewise to be proved: Iceland and East- 
ern Greenland have become much colder since the fourteenth century, for 
in the first-named country the large trees have ceased to grow, and on 
the opposite shores of Greenland a number of valleys formerly inhabited 
have become completely inaccessible in consequence of being invaded by 
ice. However it may be, we can not doubt that climates are incessantly 
modified in a more or less sensible manner over all points of the terres- 
trial surface, since the physical phenomena from which the unequal dis- 
tribution of temperature in part depend are themselves incessantly chang- 

* See The Earth, the section entitled Snow and Glaciers. 

t Hann, Zeitschrift fur Meteorologie von Carl JelineJc, vol. i., 1867. 

t Fritsch, Zeitschrift fur Meteorologie von Jelinek, No. 18, 1867. 



PAST CHANGES OF CLIMATE. 



355 



ing. The mountains, the mass of which arrests the winds, contribute to 
the formation of clouds, and attract snow and rain ; further, they are 
lowered little by little by denudation, and their materials seiwe to fill up 
the lakes, and to throw long peninsulas out into the «ea ; rivers change 
their course, and their volume of water increases or diminishes; marshes 
are dried up, while others are formed in the midst of plains ; continents 
sink or rise ; here archipelagoes show themselves above the ocean, else- 
where islands are swallowed up ; maritime currents and the winds are in 
a perpetual change. As the fossil remains of earlier faunas and floras at- 
test,* strong climatic oscillations have taken place at each period in the 
history of the earth, and cycles of heat and cold analogous to our annual 
seasons of winter and summer have succeeded each other in the course of 
ages. Without it being necessary to admit a change of axis and varia- 
tion of terrestrial latitude, we may aflirm that the present epoch, like the 
past, also presents in its climates a whole series of successive changes, 
and even history proves that the labors of mankind have a very large 
share in these very important modifications of the condition of our globe.f 

* See The Earth, the section entitled The First Ages. 
t See below, the section entitled The Works of Man. 



PART III.-LIFE. 

BOOK I.— THE EARTH AND ITS FLORA. 



CHAPTER I. 

THE ASSEMBLAGE OF LIVING CREATUEES. — NUMBER OP VEGETABLE SPECIES. 

PROPORTION OF DICOTYLEDONS, MONOCOTYLEDONS, AND CRYPTOGAMS. 

FORESTS AND SAVANNAS. 

From the simple harmony of its forms, the regularity of all its external 
features, the purity of the air which surrounds it, and the light which 
colors it, the surface of the planet is, as a whole, of magnificent beauty; 
but that which lends especial grace and charm to the earth is the infinite 
number of organisms which people it. It is these which add such a mar- 
velous variety of aspect and such great animation to the cold majesty 
which the bare face of the rocks presents, such as we still see here and 
there in desert regions destitute of vegetation. Light, heat, electricity, 
and magnetism, which give rise to so many changing phenomena in the 
life history of the world, develop centres of activity in that world of veg- 
etable and animal life which the creative force of the elements engenders 
by a mysterious transformation. Hundreds of millions of different spe- 
cies, composed of innumerable particles, w^hich are continually in a state 
of transition from the living animal to the earth, and from the earth to 
the living animal, germinate, grow, and die, to give place in their turn to 
other numberless generations of organisms. Thus multitudes succeed to 
multitudes, in the immense series of ages. The upper strata of the earth 
are renewed by all this matter which has lived. The coal-measures, the 
chalk, and the numerous other strata of limestone, which present in many 
places several miles of thickness, and thus constitute a very important 
part of the frame-work of our globe, are nothing else than the remains of 
plants and animals that formerly inhabited the land and the ocean. In 
our days, too, new layers, composed entirely of the remains of organized 
bodies, are constantly being formed, and almost the whole surface of the 
land is covered with humus or vegetable soil, formed by the destruction 
of life, which produces life in its turn. # 

It is chiefly plants which aid the formation of this nutritious earth, and 
thus prepare, centuries beforehand, the food of generations to come. In 
looking to the origin of life, we find certain undecided forms, termed by 
Carus " proto-organisras," which seem to partake at the same time of the 



THE ASSEMBLAGE OF LIVING CREATURES. 357 

nature of the animal and the plant ; but on developing, they soon exhibit, 
by their structure and mode of life, the kingdom to which they belong. 
It is the vegetable kingdom in particular that peoples and embellishes our 
earth, thanks to the abundance of its species, the richness of its forms and 
coloi's, and the vast dimensions of its trees, some of which, like the Sequoia 
and the Eucalyptus, rise to more than three hundred feet high into the 
region of the clouds. But how does the planet produce the innumerable 
living bodies on its surface, from the green conferva, which germinates on 
ponds, to man, who, proud of his strength, bravely meets his destiny V 
This is the great problem which excites the attention of the learned, and 
which is not, perhaps, altogether insoluble. The subject has given rise 
to much discussion, and to many experiments by .chemists and biologists, 
without at present any definite result being arrived at. 

Botanists have not yet had time to count the prodigious number of 
plants which surround us, from the great oak, with spreading foliage, to 
the humble lichen, spread on the ground like a stain of blood. Besides, 
if the multitude of the vegetable species have not yet been computed, it 
must also be said that they are not yet agreed on the definition of spe- 
cies, some seeing simply varieties where others find absolutely distinct 
characters. A century ago, Linnaeus knew only 6000 species ; the lists 
have since gradually increased in proportion as the various regions of the 
earth have been more and more explored, and now the total number of 
plants contained in the herbaria is estimated at about 12,000;* the in- 
crease has thus been, on an average, about a thousand each year. As to 
the numerous species which botanists have not yet classified, nof even dis- 
covered, we can only judge by proportion of the probable figure. It is 
thus that M, Alphonse de Candolle has been able to fix, in a general man- 
ner, the number of 400,000 to 500,000 species (250,000 being phanerogams) 
for the whole of the terrestrial flora. Up to our days, therefore, hardly a 
quarter of our riches has been recognized in the great inventory of the 
vegetable productions of the globe ; and not a year passes without im- 
portant discpveries being made by travelers in different parts of the 
world. Even the best known countries of Europe, which botanists have 
not ceased to explore for a century, present every year new species to for- 
tunate collectors of plants. 

Of the number of classified species, already so considerable, the greatest 
part, or about two-thirds, is composed of dicotyledonous phanerogams — 
that is to say, of plants with visible flowers, and springing from the ground 
with at least two primordial leaves : these are the highest species of the 
vegetable series. Of the third which remains in the whole of terrestrial 
vegetation, about a half consists of monocotyledons — that is to say, of 
plants which have also apparent flowers, but which spring up with a sin- 
gle seed-leaf: such are palms, grasses, reeds, and sedges. Finally, the last 
sixth comprehends the acotyledons or cryptogams — that is to say, plants 
with flowers concealed or non-existent ; fungi, mushrooms, mosses, algae, 
* Charles Martins, Du Spitzberg au Sahara, p. 17. 



358 



LIFE. 



and other families of plants which germinate without any primordial leaf, 
and which, in consequence of their rudimentary organization, occupy the 
lowest place among living beings. However, the proportions between the 
three great classes of vegetable species vary in the different countries of 
the world. The great general law recognized by Humboldt', and brought 
fully to light by M. Alphonse de Candolle, is that the proportion of di- 
cotyledons increases gradually from the poles to the equator, while the 
monocotyledons and the cryptogams become relatively more numerous 
on nearing the poles. Thus warmth of climate is favorable to the dico- 
tyledons, but cold moisture is harmful to them ; and in all countries where 
rain is very abundant, the proportional number of the monocotyledons is 
increased.* 




Fig. 163.— Map showing treeless Regions around the North Pole. 

A question still more important to man is, to know what relative ex- 
tents are occupied on the surface by absolutely barren spaces, herbaceous 
regions, and forests of great trees. Districts entirely destitute of plants 
are very few ; deserts, and even changing dunes, have their special floras, 
* Alph. de Candolle, Geographie Botanique Raisonn^e, vol. ii., p. 476. 



The Oceaa,&c 



FO R E ST S OF THE V S G ES 



PL.XDC 




LIMITS OF AUBOREAL VEGETATION. 359 

aud even the abrupt walls of rocks are covered in many places with an 
incrustation of lichens. Thus, during the rainy season, the Black Kocks 
of Pungo Audongo, in the country of Angola, appear covered with an im- 
mense drapery of velvet, which is nothing else than a net-work of an in- 
finite number of algse. When the heat comes, these coatings are dried up 
and peel off, causing the gray and yellowish lines of the rock to re-appear.* 
We may therefore consider the earth as practically clothed with plants 
throughout its extent; but it is most important to know the part of its 
surface which is* shaded by trees. This is an estimation which has not 
yet been made, although it presents the highest interest, from its connec- 
tion with the study of the variation of climates and the history of human- 
ity. If we assign to all the forests a surface equal to that of a quarter or 
fifth part of the land, this is only a hazardous approximation. Botanists 
have confined themselves to tracing on the north of the continents the 
limits which polar cold fixes for trees. This limit is found in Scandinavia 
between the 70th and 71st degree of latitude, which is not passed by the 
birch-trees ; in Siberia, the larches, which are the hardiest trees of the 
country, advance as far as the 68th degree; in North America, the firs 
grow on the banks of the Coppermine River up to the latitudes of 68 and 
69 degrees, and in Labrador up to that of 58 degrees. To the south of 
this frontier of arborescent species no country is absolutely deprived of 
trees, and even the southern extremities of the continent which advance 
in the direction of the Antarctic \io\e have extensive forests. 

Certain wooded surfaces of uninhabited countries have no less than sev- 
eral hundred thousand square miles in a single stretch. Formerly, too, 
the greater part of the regions inhabited by civilized men bore vast for- 
ests, which the axe and fire have since greatly thinned. Gaul was cov- 
ered with trees from the ocean to the Mediterranean, and the cultivated 
lands were simply clearings, like those of the American pioneers in the 
solitudes of Michigan. The Vosges, a chain of French mountains which 
is still wooded along the greater part of its extent, was a " Black Forest " 
like the corresponding system which rises on the other side of the valley 
of the Rhine.' In Germany, the great Hercynian forest had, according to 
the testimony of Roman writers, a length of sixty days' march, and now 
there remain only fragments scattered over tl^ sides of the mountains. 
Scandinavia, Transylvania, Poland, and Russia still present very vast 
wooded tracts, estimated in some districts at nine-tenths of the surface, 
the towns and villages occupying mere " clearings." But there, too, the 
work of clearing is accomplished with great rapidity. History and per- 
sonal examination teach us also that, in consequence of the diversity of 
the combined influences of heat and moisture, the contrast between the 
steppes of^rass and the great forests was formerly as great as it is now 
in Louisiana between the savannas and " cypress groves," and in the 
plains of the Amazons between the llanos and selvas. The vast sea of 
grass succeeded without transition^i^io the immense forests ; the flowery 
* Friedrich Wehvitsch, Ausland, No. 16, 1868. 



360 



LIFE. 



^o°w.orra5s 




Fig. 164. — Forests of Transylvania. 

surface of the " Tchornosjoin "* extended over half of Russia, while the 
other half was a boundless forest, intersected only by lakes and rivers. 
Nowadays the labor of the agriculturist consists especially in mixing the 
species of plants, and alternating, often in an ungraceful manner, woods, 
fields, and meadows.f 

* See The Earth, the section entitled Plains. 

t See below, the section entitled The Work of Man. 



INFLUENCE OF TEMPERATUME. • 3(31 



CHAPTER n. 

INFLUENCE OF TEMPERATURE, MOISTURE, AND SOLAR RATS ON VEGETA- 
TION. DISTRIBUTION OF PLANTS. 

Each plant has its special domain, determined not only by the nature 
of the soil, but also by the various conditions of climate, temperature, 
light, moisture, the direction and force of winds, and of oceanic currents. 
During the course of ages the extent of this domain changes incessantly, 
according to the modifications which are produced in the world of air, 
and the limits of the region inhabited by the various species are dove- 
tailed into one another in the most complicated manner. The flora indi- 
cates the climate ; but what is the climate itself, in the apparently con- 
fused mixture of phenomena which compose %t ? The preponderating in- 
fluence is naturally that of temperature ; nevertheless, we must not think, 
as most botanists did till very recently, that the limits of the zone of veg- 
etation of each plant are marked on the continents by the sinuosities of 
the isothermal lines. In fact, as Charles Martins* and Alphonse de Can- 
dollef remark, each plant requires for its germination and development a 
certain amount of temperature, differing according to the species. With 
some, life resumes its activity after the sleep of winter, when the ther- 
mometer marks three or five degrees above the freezing-point; others 
need a heat of eighteen, twenty, or even twenty-five and thirty-five de- 
grees, before taking the first step in their career of the year. Each species 
has, so to say, its particular thermometer, the zero of which corresponds to 
the degree of temperature when the vegetating force awakens its germs. 
It is, therefore, impossible to indicate by general climatal lines the limits 
of habitation for such or such species, since each one of them has for the 
commencement of its vital period a different starting-point. 

In order to know the heat necessary for plants, it would be needful not 
•to seek for the average result of the alternations of heat and cold during 
the various seasons, but to estimate the number of hours during which 
the temperature is maintained above the degree which is for each plant 
the initial point of its development. It is -true that, in this estimation, 
the relative number of hours of the day and night are not taken into ac- 
count, each of which must certainly inffuence vegetation in a diflTerent 
manner; but such as it is, this calculation is still the truest that it is pos- 
sible to establish, especially for the annual species which exist only in 
germs during the winter, and which have not, like trees and perennials, 
to protect their trunks and branches against the severity of the cold. 
Thus the climates of London and Odessa, which resemble one another so 
little in their summers, winters, and extremes of temperature, are never- 

* Voyage en Scandinavie, p. 89. t Geograpkie Botanique Raisonnee, p, 36. 



362 



LIFE. 



theless the same for vegetable species, whose development commences at 
seven or nine degrees above zero, and which require the same sum total 
of heat to arrive at maturity. Even climates so distinct as those of Edin- 
burgh and Moscow, Stockholm and Konigsberg, London and Geneva, must 
produce the same effects on plants which, starting at a certain deo-ree of 
the thermometer, require the same quantity of heat in a longer or shorter 
space of time. It results from this, that the areas of habitation of the 
species have the most various outlines. While on the side of the North 
Pole the limits of the common co\vca}^miQ-{Aq%iilegia ^vulgaris) and the 
Campanula erinus approach very nearly the course of the isothermal 
lines of Europe, the frontiers of other zones of plants traverse the continent 
in all directions, so that it is as impossible to find the least appearance 
of parallelism in them as in the lines of equal temperature. We may 
quote, as examples, the curves described by the polar limits of certain 
well-known trees and shrubs— the holly, the- Chammrops humilis, the beech. 




20 30 



..._ twis isothermal ai.S'&^atlQo 
Fig. 165. — ^Map to show the Distribution northward of Aquilegia vulgaris and Campanula erinus. 



AA Limits polar qfAqttilc^iay vuZqaris 
£JB M " ofCampimiiln/ ertmos 



ash, and jasmine. Among the plants of Europe there are even some whose 
limits indicate an absolute antagonism between the climatal conditions 
which are necessary to them. Thus the Dahoecia polifolia, a delicate 
plant which fears the cold winters and hot summers, only quits the Azores, 
with their moist and equable climate, to venture on the Atlantic coasts 
of Portugal, Spain, France, and Ireland, where rains are abundant and the 
cold is tempered. The dwarf almond, on the contrary, spreads itself fear- 
lessly from the banks of the Danube to the foot of the Ural Mountains 
across the Russian steppes, where dry and very cold winters succeed to 
excessive heat. 



AMOUNT OF HEAT NEEDED BY PLANTS. 



363 



According to the method of observing temperatures first indicated by- 
Reaumur, and subsequently supported by Boussingault, Gasparin, and 
particularly by Alphonse de Candolle, we are enabled to explain the sin- 
uosities which the limits of vegetable areas present. This method, based 
upon observation, consists in computing the " amount of heat " necessary 
to the complete development of each plant — that is to say, in calculating 
daily the degrees of average heat which exceed the temperature at which 
the plant has commenced its life for the year, and reckoning up the sum 
total of these daily heats. Certain plants belonging to the frigid zone, 
which can gCTminate and expand their leaves and ripen their fruits in a 
few days of polar summer, are satisfied with a sum of ninety degrees. 




AA Limits potarj of fu>Ui/ 
BE " n of the, ash 

CC « o £fthef beechj 



D D Limits potars ofcha^naeropsJuaraJlis 
Lines isotAermai a£ S°& at- 20" 



Fig. 166.— Polar Limits of the Holly, Ash, Beech, and of Chamoerops Humilis. 

Barley, which of all the cereals advances farthest in the direction of the 
pole, enters its period of growth when the temperature has exceeded at 
least nine or ten degrees, arid, in order to arrive at maturity, demands a 
sum of 1800 degrees, whatever may be the average of the seasons it passes 
through. According 'to Seynes, wheat commences vegetation at twelve 
degrees above zero, and receives about 3600 degrees till the time of har- 
vest, which varies according to the climates. The maize, a more souther- 
ly plant, requires a sum of 4500 degrees, and its starting-point is at the 
fifty-fifth degree of the thermometer; while the vine demands 4850 de- 
grees, commencing with the fiftieth degree of the scale. Finally, Alphonse 
de Candolle considers that the date-tree needs a total heat of about 9200 
degrees before it can ripen its fruit.* The greater part of the plants of 

* Geographie Botanique Raisonnee, p. 396. 



364 



LIFE. 



the temperate zone can support cold of twenty-eight degrees, twenty-nine 
degrees, or even thirty-six degrees, without their vital force being de- 
stroyed, but none can germinate or grow at temperatures below the freez- 
ing-point. In the mountains, saxifrages and soldanellas flourish even un- 
der the snow ; but the water which supplies their roots and the air which 
surrounds their stems have a temperature above freezing-point. The re- 
searches of Alphonse de Candolle show that the growth of vegetable spe- 
cies commences, on an average, at forty-one degrees in the regions of 
Western Europe. Still, we can not say that in the starting-point of the 
growth of each jalant we have an absolutely fixed limit like*the degree of 
temperature at which metals begin to melt ; it is probable that, according 




, Zinas isothermal acS? Sbai^JO" 



AA. Omits polar (iPf/abofdcupo^/hliai 
3B 'z II of^AmifqdaZus nanoy 

Fig. 167. — Polar Limits of Daboecia polifolia and of Amygdalus nana. 

to their vigor and their various surrounding conditions, certain individuals 
are quick and others slow to spring forth. Besides, under climates al- 
ways spring-like, as that of Madeira, plants only commence their annual 
development after having reposed during a certain period, in order to 
have time to renew their tissues. Thus the vines of Madeii'a only begin 
to vegetate toward the end of March, when the temperature is already 
64'4 degrees centigrade ; though during all the winter the average heat, 
which does not descend below 63 '5 degrees, would have been more than 
sufficient to develop the vine and cause its fruit to ripen. In the same way 
on the plateaux of tropical countries, where a perpetual spring is enjoyed, 
the plants repose during the winter period ; they preserve their leaves, but 
they do not produce new ones ; they develop flowers and fruit, but only 
those of which the buds have already germinated during the summer.* 

* Karsten. 



ACTION OF THE SOLAR RAYS. 355 

The relative dryness or moisture of the various countries is also among 
the principal causes of the limitation of the areas of species: a too rainy 
atmosphere drowns the plant ; the want of aerial vapors burns it up. 
Thus many plants do not penetrate into the dried-up steppes of Russia, 
where the temperature would otherwise be favorable to them ; others can 
not be acclimatized to the west of Great Britain, where the annual quan- 
tity of rain is enormous. The species which are developed in these moist 
countries have a charming freshness : the aspect of the trees and meadows 
shows that they are incessantly watered by rain. In tropical countries, 
where the annual heat is always sufficient to cause the plants to arrive at 
maturity, it is the influence of moisture which preponderates. The limits 
of the zone of rains are also the limits of the zone of vegetation. 

Light, as well as heat, is one of the most important conditions of vege- 
table life. Alphonse de Candolle has ascertained by direct experiments 
that of two plants sown on the same day, that which is exposed to the 
solar rays is contented with a smaller amount of heat to develop and 
ripen. It is thus to the gi-eater intensity of light that a number of 
mountain species owe the rapidity of their growth, their brilliancy, and 
the relatively large size of their flowers. On all the mountain tops of the 
south of Europe the Alpine plants, in order to grow and come to matu- 
rity, are satisfied with a much less amount of heat than the species inhab- 
iting the plains situated at a great distance to the north.* 

Another fact much less studied, but perhaps not less important than 
that of heat, contributes to the unequal distribution of plants; this is the 
chemical power of the solar rays. It would be quite natural to think 
that this power increased from the temperate to the tropical zone propor- 
tionally to the force of the sun ; however, judging from several photog- 
raphers who were not able to obtain their proofs so easily under the 
dazzling sunlight of South America as in the changeable climate of En- 
gland, it Avas, till quite recently, doubted whether the chemical power of 
these rays increased in the direction of the equator. At length Mr. 
Thorpe has removed these doubts by observations made at Para, on one 
of the arms of the River Amazon. The averages of chemical intensity 
are from seven to thirty-four times greater at Para than at the Kew Ob- 
servatory ; but while in England this intensity slowly increases and di- 
minishes each day without abrupt transitions, under the tropics it changes 
in the most sudden manner in the rainy season. When the showers ac- 
companied by electi'ical discharges fall all at once from the sky, the chem- 
ical intensity ceases completely, and then acts again with great force as 
soon as the storm has spent itself f ^ 

Under temperate climates abrupt variations of chemical light are less 
frequent than in tropical countries ; but nevertheless they are much strong- 
er than the variations of heat. In fact, from the month of December to 
the month of June, differences from one to twenty have been ascertained 

* A. de Candolle, Geographie Botanique Raisonee, p. 310, and following. 
t lloscoe, Lecture at the Royal Institution. 



866 LIFE. 

in England and Germany in the activity of the luminous rays. This is be- 
cause the influence of these rays does not only depend on the position of 
the sun in the heavens, it increases or diminishes according to the innu- 
merable changes which ai-e effected in the atmospheric ocean. Thus the 
whitish clouds which veil the sky like light draperies, give a greater chem- 
ical force to light, and the effects make themselves immediately felt upon 
nature ; but if the clouds thicken, and interpose themselves in black mass- 
es between the sun and the earth, then the action of the luminous rays 
immediately decreases, and a sudden ebb succeeds to the full tide of vital 
force which was distributed from the sky.* 

With the perturbations in climate which produce the incessant altera- 
tion of clouds, fogs, and invisible vapors, we must include the changes 
caused by the myriads of grains of dust and floating germs, and by all 
the emanations of carbonic acid, hydrogen, and ammonia which escape 
from the earth and disturb the purity of the air. It is thus very diflicult, 
in the present state of science, to indicate approximately, even for the 
best-known countries of Western Europe, the relative value of the chem- 
ical action exercised on an average during the year by solar rays. It 
would be still more difficult to trace on the circumference of the globe 
isochemical lines analogous to the isothermal lines. This is a conquest 
of science reserved for future observers. Nevertheless, the researches of 
Messrs. Bunsen, Roscoe, and other savants have already proved that the 
power {p actinite) of the solar rays is subject to greater modifications than 
the heat ; the lines of equal chemical climate must consequently much ex- 
ceed the lines of equal temperature in their curves and abrupt windings. 
If there are no chemical winds like moist and warm winds, it is precisely 
these latter which incessantly modify those changing masses of vapor in 
the atmosphere which alternately diminish and increase the force of the 
sun's rays. 

Thus the extraordinary difference between the floras of two neighbor- 
ing countries the temperature of which is visibly the same, may perhaps 
be explained by the enormous influence which the state of the sky exer- 
cises. Thus flowering shrubs do not grow in the Faroe Islands, and we 
only see brush-wood and meagre bushes there, although the temperature 
is only one degree below that of Carlisle, in England, where we have fine 
forest vegetation. In fact, if the heat is the same, the light is very differ- 
ent. The sun's rays which penetrate the mists of England are in great 
part absorbed by the thick fogs of the Faroe Islands, which the ancient 
navigator Pytheas believed to be a sort of "marine lungs," where air, wa- 
ter, and mud were confusedly mingled. Perhaps, too, it is to a greater 
chemical and luminous force develoj^ed during the long days that we 
should attribute the singular rapidity with which the plants of the north 
shake off their winter sleep at the time of the sudden invasion of spring. 
In a few days all the trees are covered with buds and leaves, while months 
elapse, in more southerly latitudes, between the budding forth of the dif- 
* Rod. Radau, Revue des Deux Mondes, 1st November, 1866. 



ACTINIC SUN-EATS. 357 

ferent species. Not only do the plants indigenous to the north, but those 
nlso which are acclimatized in these regions, open their buds much sooner 
than might be expected according to the habits of these plants in south- 
ern countries. At St. Petersburg, under the sixtieth degree of north lati- 
tude, it has been ascertained that the budding of the birch-tree, the first 
signs of spring-tide life, precedes that of the lime-tree by five days, and 
the flowering of the common Alchemilla by only eighteen days ; while at 
Breslau, situated eight degrees fiirther to the south, the intervals are re- 
spectively fifteen and fifty-one days.* "The farther we advance to the 
north," says Alphonse de Candolle, " the more does light replace warmth 
in utility." 

Thus we see the questions relating to the natural areas of plants are 
most complicated, and that it is not without very long and jjatient study 
that botanists are able to determine precisely what are the natural history 
and distribution of each plant, and what are the manifold causes which 
arrest its extension beyond certain limits. Not only must we take into 
account the alterations of temperature, light, and of the chemical power 
of the solar rays, but it is necessary also to estimate the effect of all mete- 
oric phenomena, to appreciate the influence of dryness and moisture, of 
long rains and j^assing showers, of exposure, of different altitudes and of 
♦inequalities of the ground. Besides all these conditions of the climatal cir- 
cumstances, it is necessary also to know what is the vitality belonging to 
the plant itself, what its power of distribution over the .earth, and the 
strength of its resistance to the destructive agents which surround it. It 
is also important to know the foi'mer disti'ibution of continents and seas 
in geological times, so as to learn what obstacles, such as arms of the 
sea or. chains of mountains, may have arrested the distribution of certain 
plants over more extended areas. Each plant has its separate history, its 
peculiar characters and geographical distribution; and thus it is to the 
extreme diversity of the conditions of existence that we owe the wonder- 
ful variety which is presented by the grouping of species on the surface 
of the globe. 

* Auton von Etzel, die Ost See, p. 239. 



LIFE. 



CHAPTER III. 

PAETICTJLAE HABITATS OP SPECIES. — SALT-WATEE AND FEESH- WATER 

PLANTS. — LITTOEAL SPECIES. — PAEASITES. TEEEESTEIAL SPECIES. IN- 

ELUENCE OF THE SOIL ON VEGETATION. PLANTS ASSOCIATED TOGETH- 

" EE. SEA- WEED. EXTENT OF AEEAS. « 

Most plants occupy but a small portion of the space circumscribed by 
the general limits which climate has traced for their habitation. This is 
because, according to their nature, certain special physical conditions are 
also necessary to them, without which germination and growth are impos- 
sible. Thus, to cite the most striking example, the aquatic vegetation is 
composed of species quite different from those which grow on dry land. 
Excepting in the undecided zone altei-nately covered and laid bare again 
by the waters, and where plants called amphibious are developed, the two 
floras are absolutely distinct. If it be true, as certain botanists think, 
that some kinds of marine algse produce terrestrial plants of the mush- 
room tribe, the germinative power would in this case only exercise its 
force to transform completely the structure and appearance of the plant. ♦ 

The contrast of the floras is scarcely less absolute between fresh and 
salt water than between the seas and the continents. The ocean has its 
special plants, some floating freely over the waves like the sargasso, or 
" grapes of the tropics," others clinging to the rocks and ledges of the 
shore. The rivers, lakes, and ponds of fresh-water have also their partic- 
ular species ^ potamogetons, swaying like, long hair at the will of the 
current ; water-lilies, spreading their broad leaves of an emerald green 
over the transparent water ; innumerable confervse, forming a continuous 
layer of vegetable matter on the surface of the pond, resembling from 
afar the surface of a meadow. The plants which flourish equally in fresh 
and in salt water are very few, and usually are only met with in the estu- 
aries of rivers where the tide ascends, and where the mingling of the wa- 
ters takes place. As to the turbaries, they are entirely composed of a 
particular set of plants which press against each other, and contain wa- 
ter in their interstices as in an immense sponge.* The vegetation of the 
shores themselves presents one of the most striking contrasts, according 
as they surround fresh-waters or seas saturated with saline substances. 
Thus the deposits of the ocean, the sand or clay of which is strongly 
charged with sea-salt, produce in abundance sassify, samphire, thrift, and 
other plants generally of a somewhat dull appearance, which give a spe- 
cial physiognomy to the shores. In the interior of continents a similar 
flora is only found around salt lakes and in districts where springs of salt- 
water rise from the earth ; it is indeed the sight of these plants which 
has often urged miners to pierce the soil, so as to discover there banks of 
* See The Earth, the section entitled Lakes and Marshes. 



Tke Ocean. Ac. 



SARCA 







-4^ 




m 


••> ••... 


#' ..■• 


1 m 


%-^ 


y • •:• 


4 


V*.. .•■•■.■ 




^ .• . 


r.; ■ •■■;- 




- '^.. 


'' ^ 



• •• 



• • • ••••••• • 




Eng^by ET-linril 



HAR.PER. 8c BRC 



SEA. 



PL. XX 








» .• .*? 



•'.•.i 



C^,.VKTU>t^ ^. ^^^^^, 



aMAooa 

mm 



js'-- 



Arranged iJvAyiiillenriTi after M^.'Lpps 



•S. NEW YORK 



CHOICE OF LOCALITY BT PLANTS. 3O9 

rock-salt hidden in the depths of the ground. Other kinds of j^lants seem 
to require not the sea-salt but the vapors which escape from it. Such is 
the case with one of the most charming heaths, Erica sylvatica^ which 
grows in the low plains around the Gulf of Finland, the Baltic Sea, the 
North Sea, the Channel, the Bay of Biscay, and which is found also on the 
coiasts of Spain and Portugal, without ever having been met with at more 
than one hundred and fifty miles from the shore. 

The atmosphere possesses its special vegetation, as 'well as the waters. 
Certain plants demand from the earth simply a support, and draw from 
the air all the nourishment they require. Multitudes of other species 
never grow on the bare earth, but fix themselves on the hidden roots, 
stems, or branches of other plants, which serve as a nourishing soil to 
them. Lianas of all sorts, orchids, passion-flowers, bignonias, euphorbias, 
apocyneas, ferns, mosses, and lichens, group themselves thus into aerial 
forests, and, mixing with the foliage of the trees which bear them, adorn 
them variously with garlands, bouquets, tufts of verdure or flowers. Upon 
these parasites other parasites live ; and in certain tropical forests, where 
each tree is a whole world of plants, the foliage of the interlacing vege- 
tations presents such a confusion of forms that the eye of a most expe- 
rienced botanist alone is capable of distinguishing them. 

Finally, even the interior of the soil has its particular flora, composed 
of trufiies and other cryptogams, which only receive the influence of the 
atmosphere through the fissures of the earth. Grottoes, too, to the very 
end of their labyrinths, have plants which shun the light, and in the for- 
ests certain species of vegetables, almost always white or pale-colored, 
hide themselves in the shadow at the foot of the great trees, and raise 
their delicate stems above the carpet of moss and dry leaves. 

Among the much more numerous plants which bury their roots in the 
ground and wave their leaves in the open air, there are some which prefer 
a sandy soil; others grow best in a limestone country; others again on 
gravel, stifl" clay, or in the fissures of granite. Some botanists have even 
attempted to class plants according to the chemical composition of the 
soil they affect. It is certain that many kinds, even without counting 
those which grow on salt lands, are met with exclusively on their favor- 
ite|*oil. The chestnut, the purple foxglove, and the common broom de- 
light in a siliceous soil ; the Carex arenaria, and other ordinary plants of 
dunes, and, under tropical climates, the cinnamon-tree, require almost pure 
sand; limestones have also their species, which do not thrive elsewhere. 
Nevertheless, it does not seem to be so much on account of the substan- 
ces which they contain, but rather because of their physical properties, 
such as hardness, density, and porosity, that these different soils nourish 
particular species of plants. If the composition of the rock remain the 
same, but become at the same time more disintegrated, allowing the outer 
air and moisture to penetrate more readily, the vegetation will instantly 
change, and we shall see species appear on the chalk or clay that we might 
only expect to find on sand. Thus, when the botanist leaves a country 

24 



370 LIFE- 

where, in consequence of the resemblance of the physical conditions of the 
soil, the same rocks are always covered with the same vegetable carpet, 
he perceives with astonishment that species forsake the soil which he be- 
lieved to be necessary to them. Of forty-three plants which Wahlenberg 
had only observed on the chalk in the Carpathian Mountains, he found 
twenty-two on the crystalline rocks of Switzerland and Lapland, Similar- 
ly, of sixty-seven species which in Switzerland exclusively grow on calca- 
reous ground, thirty-six are found in the surrounding countries on soils 
the chemical composition of which is quite different ; and one might be- 
lieve that further researches would result in reducing still more the num- 
ber of plants which are absolutely peculiar to one kind of soil,* Besides, 
as M. Theodore de Saussure has proved, the tissue of many plants seizes 
hold indifferently of the most abundant and most soluble substance which 
is found round the roots : the ashes of the Norwegian fir are not of the 
same composition as those of the fir-tree of the Jura, 

Not- only do species of plants know how to choose the soil that best 
aids their grow.th, but they also seem to exercise a kind of discrimination 
in their associations with other plants ; either it is that they demand ex- 
actly the same physical conditions of soil, or else that they seek a shelter. 
Without speaking of the parasites which have no independent life, a num- 
ber of" social" species are always near together, and, by the harmony of 
their grouping, impart some sweetness and friendliness to nature. Thus 
the approach to a forest is announced to the traveler by little plants and 
shrubs which do not grow in the open country ; the gay colors of blue 
corn-flowers and poppies are always mingled, at least in Western Europe, 
with the light ears of corn; herbs that agriculturists qualify as " weeds" 
associate themselves invariably with the crops in our fields; plantains and 
potentillas grow together on the road-side, and, so to say, under the very 
feet of men ; the chalets of the Alps and Pyrenees are surrounded with 
nettles and docks which rise in tufts above the short grass of the pastures. 
Finally, the grassy steppes, American prairies, savannas, or pampas, are 
nothing else than immense colonies of social plants. By contrast, the des- 
erts, with their burning soil, often present over vast areas only the mea- 
gre verdure of a single species of plant. Thus the clay of the plateau of 
Utah only allows the roots of an artemisia to penetrate into its fis^res, 
and over a great part of their surface the deserts of New Mexico and Ar- 
izona have, as their sole vegetation, only the gloomy and fantastic cande- 
labra of the giant taper.f 

The ocean, like the earth, has its monotonous tracts of plants ; there are 
whole fields of sargasso {Fucus natans), which are found in the centre of 
several maritime basins, and notably in the immense triangular space com- 
prised between the Antilles, the Gulf Stream, the group of the Azores, and 
the archipelago of Cape Verd. Columbus .crossed these parts filled with 
marine plants ; and for his companions it was not the least among their 

* Alph. de CandoUe, Ch. Martins. 

t See The Earth, the section entitled Plains. 



OCEANIC VEGETATION. 37 1 

terrors to see these long runners which retarded the progress of the ship, 
and made the unlfcthomable sea appear like an immense marsh. Inter- 
laced in floatiiiawslands and islets which follow each other in intermina- 
ble procession^^hese plants change the surface of the ocean in certain 
places to a kind of meadow of a greenish-yellow or rust-color ; the waves 
raise these masses in long undulations, and surround them with borders 
of foam ; fish sport by hundreds under this vegetation, which shelters 
them from the sun ; myriads of little animals — crabs, shrimps, serjjulae, 
and shells, run, climb, and incrust themselves on the interlacing stems of 
these migratory forests, and traverse with them the extent of the seas. 

It was formerly believed that this floatin^weed of the Atlantic had 
been detached by the breakers from the shoi^Pof the Antilles and Flor- 
ida, and then carried hundreds of leagues from land by the Gulf Stream. 
All these masses, borne along the course of the waters, would be at last 
united, as in the centre of an eddy, in the space surrounded by the waters 
of the great circular tourbillon of the North Atlantic, This notion was 
not correct ; the fuel of the ocean originate and are developed on the sur- 
face of the waters. Neither roots nor the least indications of bulbs can 
ever be discovered in them which could have clung to the earth, and 
which the waves might have torn away. Each stem is abruptly termina- 
ted at its lower extremity by a kind of cicatrice, and is evidently only a 
detached* branch of another plant; vesicles full of air, which have given 
this fucus the name of the " tropical grape," serve as floats to sustain it 
on the water, while hundreds of foliacTOus membranes rise vertically 
above every islet of the weed, so as to absorb the quantity of air which 
these organisms require in order to grow and propagate themselves. 

It is true that all these meadows of sea-weed circulate under the influ- 
ence of the winds in the eddy formed by the Gulf Stream and the equato- 
rial current ; but instead of having been brought by these marine rivers, 
they are, on the contrary, arrested by them, and accumulate in rows along 
their inner shores. Only a small number of plants penetrate into the sea 
of the Antilles and Gulf of Mexico by channels between the islands. The 
sea of weed properly so called of the North Atlantic is comprised be- 
tween the sixteenth and thirty-eighth degrees of north latitude, and ex- 
tends from east to west, from the forty fifth to the seventy-fifth degree of 
longitude. In this immense space the weed constitutes two separate 
masses, as if a branch of the equatorial current bent toward the north, * 
and thrust back to the right and left the meadows of sea-weed. We can 
venture to estimate the surface of this sea of weed at more than four thou- 
sand square miles ; in the other oceans, the North and South Pacific, and 
South Atlantic, it covers enormous surfaces. If ever the agriculturists of 
Europe and America put into execution the idea of M. Le^ who proposes 
to load ships with this weed, they would be able to pr(mde themselves 
amply with this manure for the improvement of their crops.* 

* Leps, Annales Hydrographiques, 1857, fourth term ; Bulletin de la Societe de Geographic, 
September, 1865, Laverriere. 



372 LIFE. 

It appears, from the numerous comparative studies of Alphonse de Can- 
dolle, tliat the general form of the area occupied by ea«h plant is that of 
an ellipse a little elongated from east to west, under thfitemperate, and 
from north to south under the trojjical latitudes. This^mtural arrange- 
ment is easily understood, for in the various zones the greatest diameter 
of the ellipse ought to indicate the direction in which the climate presents 
most equality over a more considerable extent. It is a remarkable fact 
that the area occupied by the species is the more extensive the simpler 
their organization is, and that they likewise seem to possess a greater an- 
tiquity. Thus the cryptogams, which are the least developed plants, oc- 
cupy the? largest surface. In the same way marine species have an aver- 
age area more extensive ^pan that of the terrestrial species ; herbaceous 
plants occupy a more considerable area than trees ; and finally, the an- 
nual phanerogams have a country of larger dimensions than the perennial 
and woody phanerogams. " The area of plants is in inverse proportion 
to the complication of their structure." It is also very remarkable that 
from logical causes, probably anterior to the present state of the globe, 
the average area of species diminishes gradually from the Arctic Pole in 
a southerly direction. 

No kind of flowering plant, not even the nettle and purslane, the most 
faithful of the companions of man, inhabit the entire earth. Only eight- 
een species are reckoned which show themselves at the same time on 
half the terrestrial surface, and the total number of known plants, which 
each occupy a third of the gloBe, is only estimated at a hundred and sev- 
enteen. On the other hand, there are plants which botanists have never 
discovered except in a single ravine or on an isolated promontory. The 
many islands scattered in the ocean — St. Helena, Tristram d'Acunha, Juan 
Fernandez, Madeira, and the Galapagos — possess the greater part of these 
solitary plants not to be found elsewhere. But there are also parts of the 
continent where the species have their whole domain — a district of a few 
leagues or acres — which may be regarded as a sort of continental island. 
As to the general superficial extent of the areas, it would be, according to 
Alphonse de Candolle, about the hundred and fiftieth part of the earth's 
surface — that is to say, nearly 180,000 square miles. 



CONTRAST OF TEE FLORAS. 37; 



CHAPTER IV. 

CONTRAST OF THE FLORAS IN THE DIFFERENT PARTS OF THE WORLD. — IN- 
SULAR AND CONTINENTAL FLORAS. — INCREASING RICHNESS OF VEGETA- 
TION IN THE DIRECTION FROM THE POLES TO THE EQUATOR. 

Considered as a whole, the continents themselves, like the more re- 
stricted areas, present remarkable contrasts between their floras. Thus, 
taking their disproportions as to extent into account, the New World ap- 
pears to be much richer in species than the Old, This fact is explained 
by the general disposition of the two Americas, and its chains of mount- 
ains almost all running in the direction from north to south. In conse- 
quence of the i^osition of the Andes and the Cordilleras, the mountains of.,, 
Brazil, the Alleghanies, the Rocky Mountains, the Sierra Nevada, and the 
Coast Range of California, it is found that under each latitude the most 
various climates succeed each other on the opposite slopes, and, in conse- 
quence, different species are developed in each of these distinct climates. 
In the Old World it is not thus, for most of the mountain chains — the 
Pyrenees, the Alps, the Balkans, the Caucasus, Mount Taurus, the Hima- 
layas, the Karakorum, the Kuenlun, stretch in a direction from west to 
east, and consequently the climates and floras are not modified in the 
same direction, but by very gradual transitions. On the other hand, Af 
rica, notwithstanding the situation of the greatest part of its mass under 
the torrid zone, is relatively less rich than the other continents in species 
of plants. This is explained by the general uniformity of the country, the 
few high chains of mouniPns, and the very slight moisture of its winds. 
But the southern extremity of Africa, the English colony of the Cape, is 
exceedingly rich in plants. 

Another contrast has been pointed out by several botanists — that of 
the relative poverty of the insular, compared to the continental floras. 
But this question is disputed, and the want of sufficient observations does 
not allow us yet to decide it. Nevertheless, it is certain that the large 
islands, such as Great Britain, Sicily, Cuba, and Ceylon, have types of veg- 
etation entirely analogous to those of the neighboring continents ; and 
similarly, the Fai'oe Islands and Spitzbergen have as many species in pro- 
portion as the larger countries lying at an equal distance from the pole. 
The archipelago of Cape Verd, the Canaries, Madeira, and the Azores 
have, on the contrary, from three to five hundred species less than are 
found on the same continental extent. Mauritius and Reunion have also 
a relatively small number of indigenous plants; and it is quite natural to 
think, with M. de Candolle, that the poverty of these islands proceeds in 
great part from their long isolation in the open sea. 

The principal fact in the distribution of plants ov6r the surface of the 



374 -LIFE. 

globe is the increasing richness of the floras in the direction from the 
poles to the equator. Thus the island of Spitzbergen, the best explored 
of the countries of the frigid zone, has only ninety species ; while on an 
equal surface Silesia has 1300, Switzerland 2400, and Sicily, much less in 
extent, possesses 2650,* It is true that in many countries of the tropical 
zone exceptions have been ascertained to this law of the augmentation of 
species toward the equator, but all these exceptions may be easily ex- 
plained by soil and local climates. The Sahara has certainly a flora much 
less rich in proportion than that of Southern Europe ; but then what a 
difference there is between these two regions in regard to the physical 
configuration of the surface ! If Egypt has only 1000 plants, while Great 
Britain, situated much more to the north, presents on an equal extent 
1480, it is because the Valley of the Nile is only a narrow alluvial land, 
bounded on the one side by sand, and on the other by rocks destitute of 
moisture. Without being deceived by the relative poverty of the Egyp- 
tian vegetation, even the Greeks asserted that the number of plants in- 
creased more and more toward the south ; they even added this fanciful 
detail, that in the burning countries of the south the ground sank under 
the enormous weight of the trees that it supported.! 

linger has proposed to divide the surface of the eai'th into different 
zones of vegetation, succeeding each other symmetrically from the two 
poles to the equator. The northern polar zone, to which a still unknown 
southern pole corresponds, comprehends the icy archipelago of America, 
Greenland, Spitzbergen, and Northern Siberia. Forests are entirely want- 
ing there ; thus, as Linnaeus says, the lichens, "'the lowest of the vegeta- 
bles, cover the last land." To the south of this extends the arctic zone, 
where the first trees and the first crops show themselves. Next comes 
the sub-arctic zone of British North America, Iceland, and Northern Rus- 
sia, characterized by peat-bogs, toundras, andlforests of pines, fir, larch, 
and birch trees. The cold temperate zone, the southei'n limit of which is 
found near the forty-fifth degree of latitude, also presents regions of peat- 
moss and forests ; but it is also the especial country for meadows, and its 
woods are composed of the most varied species. In the warm temperate 
zone the meadows become rarer, while the arborescent species gain still 
more in splendor and brilliancy. The palm-trees and bananas make their 
appearance in the sub-tropical zone ; but it is in the tropics and at the 
equator that vegetation is developed in all its marvelous richness. To 
the south of the equinoctial line the floras succeed each other in inverse 
order to the Antarctic pole. But, as we* can understand, these divisions 
are, for the most part, arbitrary, and in nature the transitions are eff*ected 
from zone to zone in a generally imperceptible manner. It is a remark- 
able fact that one of the most clearly-defined zones is exactly cut in two 
by a vast maritime basin. This is the vegetable zone which surrounds 
the Mediterranean fx*om the Gulf of Lyons to the delta of the Nile. The 

* Alph. de CandoUe, Geographie Botanique Raisonnee, p. 1287. 
t Carl Rftter, Geschichie der Erdkunde. 



m 



PECULIAB LIVING FLORAS. 



375 



7_> Jil J> 




EZ3 Plorcu-JWejiit£rrancajz/\. 
\'X. .1 — Hiuvpean/ 
tiil — Sdharijxn-' 



Fig.lGS.— The Mediterranean Flora. 

Mediterranean flora is thus a narrow circular band, developed over a lin- 
ear extent of more than 5000 miles. 

Owing to the diversities of the earth's surface, the differences of tem- 
perature and climate, owing also to those secular displacements of conti- 
nents which result in an equal displacing of floras, all countries are distin- 
guished one from the other by a characteristic vegetation. Scandinavia 
has its forests of coniferous trees, England has its oaks and its meadows, 
the north of Germany has its lime-trees, Russia its birch-trees, France its 
elms and bedftes. We can not think of even the Vosges or the Black 
Forest without recollecting those long slopes covered with firs; and 
when we dream of the Alps, we always see them in our memory with 
their clumps of walnut or chestnut trees, their forests of larches, their 
rhododendrons and their gentians. In the same way we can not imagine 
the beautiful country of Italy without olive-trees, cypresses, and maritime 
pines. The terrible monotony of the Sahara is relieved by fresh oases of 
date-trees, and toward the southern extremity of the continent, at the 
Cape of Good Hope, the harsh contours of the hills and mountains are 
enlivened by their carpet of heaths and many-colored flowers. The Uni- 
ted States have their trees with marvelous autumn tints, where all shades 
are found at the same time, from the most dazzling purple to the darkest 
green. The contrast is great between these forests, with varied colors, 
and the uniform extent of the prairies on the west, or the deserts of New 
Mexico, scattered over with cactuses. In South America, the forests of 
araucarias of the mountains of Chili and the Brazilian Plateau do not pre- 
sent a less striking contrast with the pampas and their vegetation, so rich 
in leguminous plants. At the other extremity of the world, the Austra- 



3 7 6 -LIFE. 

lian floi-a contrasts with that of the whole world by the antique appear- 
ance of its eucalyptus and its Casuarmacem, dating, perhaps, from the Ju- 
rassic epoch. The species of New Zealand are distinguished also by their 
general facies from that of all the continents. Nowhere else do we see 
so great a proportion of trees and shrubs compared with annual plants ; 
nowhere do the cryptogams present such a variety of forms. Meadows 
are wanting, but the ferns grow in immense forests, as at the epoch of the 
coal formation. The succession of terrestrial ages which the geologists 
seek in the fossiliferous strata, and which they estimate at millions of 
centuries, the botanists may see in summary at the present epoch by trav- 
ersing the surface of the globe. The floras of the past periods, stored in 
the strata of Western Europe as in an immense charnel-house, still live, 
more or less modified, in various parts of the globe, 

Vjrgin forests, where man has scarce ever penetrated, save to make a 
few paths, are among the grandest specj^acles of nature. Those of cold 
countries, composed for the most part of conifers with straight trunks 
and dark foliage, have something solemn and august in their appearance. 
The mighty shafts of the trees are planted regularly, .like the pillars of an 
immense edifice, and in the distance appear in mysterious avenues. The 
branches, widely spread and laden with grayish moss and lichens, only 
allow a diffused light to pass through their boughs, spreading as they do 
symmetrically under the vault of thick verdure. A few knotted roots 
here arid there peep from the ground, which is covered with fallen leaves 
and sown with modest plants, some clustering at the foot of the trunks, 
others grouped in masses in the open spaces. Nothing from without pen- 
etrates into this retired world, excepting it be a ray of sunlight darting 
like an arrow between two boughs, or the sighing of the wind among the 
branches. 

The gi'eat tropical forests have quite another characte%and strike us 
especially by their magnificence, the luxuriance of their vegetation, and 
the variety of their species. It is not so majestic and regular as a forest 
of firs or larches; it is a chaos of verdure, an accumulation of interlacing 
foliage, where the eye vainly seeks to distinguish the innumerable vege- 
table forms. Above the large tufted tree-tops others ai'e perceived, and 
palm-trees rise, united to each other by an inextricable net-work of li- 
anas; broken boughs, suspended by almost invisible cordage, swing m 
space; the pandanus spring like rockets of verdure from the confusion 
of branches and leaves of every variety, which are disposed in plumes, 
fans, bouquets, and garlands ; orchids expand their strange flowers in the 
air; trees which have fallen fi'om age disappear under the mass of flow- 
ers, and the greater part of those still upright are themselves surround- 
ed as with a new bark, by spiral stems of parasites with elegant foliage. 
While in the forests of the north all the trees resemble each other, and 
yet grow isolated, like the independent citizens of a free people, the innu- 
merable species of the tropical forest, so different from each other in di- 
mension, form, and color, seem to be mingled in one and the same mass 



FLORA OP THE AMAZONS. Z11 

of vegetation," the tree has, so to speak, lost its individuality in the life of 
the whole. An oak. of the temperate zone spreading its boughs with their 
rugged bark, plunging its roots into the crevices of the soil, and strewing 
the earth with its withered leaves, always seems to be an indej^endent be- 
ing even when surrounded by other oaks like it. But the finest trees of 
a virgin forest of South America are not independent. Twisted round each 
other, knotted in all directions by cordages of creepers, half hid by the 
parasites which strangle them and drain their sap, they are lost in the im- 
mense mass of vegetation which covers the entire country. 

It is from the even surface of the sea or of a great river that one ought 
to see the tropical forest, especially when it clothes the sides of an ele- 
vated hill from the summit to the base. Under this undulating mass we 
can hardly imagine the soil that supports it ; we might think that the 
entire forest was rooted in the waters, and floated like an enormous py- 
ramidal plant two hundred yards high. Where the hill presents a rapid 
declivity, great masses of branches, creepers, and their flowers stretch 
from toee-top to tree-top like the sheets of a cataract. It is a Niagara 
of vemure. A moist atmosphere, laden with the mingled scents of the 
plants, escapes from the forest and spreads itself afar ; in foggy weather 
travelers have recognized, at one hundred miles out at sea, their proxim- 
ity to the coasts of Colombia by the perfumes diffused abroad.* 

Of all these marvelously rich tropical vegetations, the most varied is 
that of the basin of the Amazons, as indeed the geographical situation of 
the country is suflicient to show beforehand ;-for nowhere else can we find 
rich alluvial soil, abundance of rain, and power of solar rays so admirably 
united over such a vast extent. Over a space of many thousands of miles 
from north to south and from east to west, the plains of the Amazons are 
nothing but a limitless forest, interrupted only by the wide channels of 
the river and its tributaries, and marshes and lagunes on their banks, 
and here and there bj^glades with high grass, where a few scattered 
trees appear. The botanist stands confounded before the immense varie- 
ty of plants which present themselves to him; while in the river itself he 
already sees a series of interlacing trunks and branches still garnished 
with their leaves, which the cui-rent carries away like a kind of floating 
forest. On the marshy soil of the shore reeds ai-e crowded together, 
which advance in promontories. On the bank, properly so called, the 
alluvium deposited each year has its particular vegetation, higher, more 
tufted, and more entangled with creepers, the more ancient the soil is on 
which it grows. Beyond this first rampart of new trees, which in many 
places hides the real forest,f the virgin solitude of the great woods com- 
mences, where the flora of the Amazons is seen in all its beauty and all its 
majesty at the same time, owing to the prodigious number of plants that 
compose it. The most varied types, climbing herbs, and gigantic trunks 
are mingled together; light creepers, suspended to the branches, connect 

* Kiddle, Nautical Magazine, March, 18G5. 
+ Ave-Lalleinant, Reise durch Nord-Brazilien. 



378 ■ -LIFE. 

in one net-work the boughs of the entire forest. This is a wonderful pic- 
ture, which ought to be contemplated in free wild nature, either on the 
shores of some lagune, where the enormous leaves and delicate rosy flow- 
ers of the Victoria regia display themselves, or else on the surface of a 
tortuous stream, all festooned with garlands of interlacing plants, which 
float beside the canoe o^ the travelers. In no country in the world are 
strength and beauty, grandeur, with at the same time great beauty of de- 
tail, combined in so happy a manner ; it is the triumph of living nature. 
The forest is at the same time grand and joyous, and has nothing of the 
melancholy of the woods of the temperate zone.* 

If all the plants of the world are not found in the vast selvas of the 
Amazons, at least all the genera, even those which are completely miss- 
ing, still have their representatives. Thus the family of Rosacem, which 
gives us the charming eglantine of our hedges and the beautiful garden 
roses, the greater number of our fruit-trees, the pear and the apple, the 
peach, cherry, medlar, almond, and many others, hardly exists under the 
tropics; but these plants are replaced by another great family, that of the 
myrtles, which produces the guava, the pitanga, and a great many Hvory 
fruits whose names are scarcely, if at all, known beyond the tropical re- 
gions. Thus each zone has its special family of fruit-trees. In the same 
way the humble cereals of the north, the grains of which serve as the chief 
food for man, have equivalents in the neighborhood of the equator in the 
great family of the palms, of which so great a number of species live on 
the banks of the Amazon and its afiiuents. Each of these rivers has its 
characteristic species of palm-tree, giving a new aspect to its -forests and 
the villages on its banks. Even on the principal river the varieties suc- 
ceed each other several times, from the embouchure to the confluence of 
the Solimoes with the Rio Negro, and higher up as far as the mountains 
of Peru.f The species of this tree, which support the natives with their 
fruit, and furnish them at the same time with refreshing water, with tis- 
sue, and with building materials, are still more numerous than the cereals 
of the northern countries. And yet the Amazonian regions are scarcely 
known even now, save in the immediate neighborhood of the river-banks, 
and each new exploration of botanists there will reveal the existence of 
new vegetable treasures. 

* Ag&s%\T,,Conversagoes Scientificas sohre o Amazonas. t Id., Ibid. 



VEGETATION ON MOUNTAINS. 379 



CHAPTER V. 

DISTRIBUTION OF yEGETATION ON THE SLOPES OF MOUNTAINS. MINGLING 

OF THE DIFFEEENT FLORAS. UPPER LIMITS OF THE PLANTS IN VARIOUS 

PARTS OF THE WORLD. IRREGULARITIES IN THE VERTICAL DISTRIBUTION 

OF PLANTS. 

In consequence of the gradual decrease of temperature on the sides of 
mountains, zones of vegetation analogous to those which succeed each 
other from the equator to the pole over the surface of the globe, are situ- 
ated one above the other from the base to the summit of mountains. By 
the flora as by the climate, we might think we were proceeding in the 
direction of the polar regions, in proportion as we ascend the sides of a 
peak at a higher altitude above the plains; but the intervals of climate 
that it would take days to cross in traveling toward the pole are trav- 
ersed in a few minutes of ascent, since in the mountains a height from one 
hundred and seventy-five to two hundred and sixty yards corresponds, 
on an average, to one degree of latitude. At the foot of the plateau 
which bears the Cayambe in the equatorial Andes, the vegetation is that 
of the torrid zone ; at the snowy summit of this volcano, which is inter- 
sected by the very line of the equator, we find plants recalling those of 
Greenland ; but to whatever height we ascend, we always find living or- 
ganisms. Above the snow itself the cellules of the Protococcus are group- 
ed and live, as in the deepest seas the sounding-lead still discovers dia- 
toms in infinite myriads. 

The limit which separates the flora of the mountain from that of the 
lowe#plains is not always very distinct, and we must often traverse vast 
debatable regions before knowing by the aspect of the surrounding plants 
what zone of vegetation we have under our eyes. In the same way it is 
very diflicult to distinguish, on the slope of a mountain chain, "the various 
floras, one above the other, because certain plants* are common to two 
zones at once, and some, from various physical causes and changes, de- 
scend below or mount above the normal region of their abode. It is thus 
that on the sides of the volcano of Chiriqui Moritz Wagner found mead- 
ows and green oaks beside euterpe-palras and bignonias.* In the same 
way, too, in the Colombian state of Santander, the banana and the sugar- 
cane flourish excellently at the height of 9000 feet, in the midst of the re- 
gion of oaks and birches. There is, therefore, not only superposition, but 
also an intermingling of climates and forests. In the Cordillera of Val- 
divia this mixture of floras is such, that trees of the plain mount almost to 
the lower limit of perpetual snow, owing to the extreme abundance of 
rain, and to the equality of the climate.f 

* Mittheilungen von Petermann, xi., 18^2. 

t Grisebach, Geographisches Jahrbuch, von Behn, ISGG. 



a 80 LIFE- 

The mountains where the limits between the zones are more clearly 
defined are, as we can understand, those whose slopes are cut in abrupt 
escarpments. A precijDitous rock some hundred yards high is most fre- 
quently a visible frontier between two floras. One may see a magnifi- 
cent example of this at the fall of Tequendama, in Colombia, where the 
water plunges from the zone of apple-trees and rye, to fall into that of the 
palms of the Mauritius. Similarly, a sudden change in the physical con- 
ditions of the place can define clearly two zones of vegetation. In Val- 
louise, not far from the foot of the Grand Pelvoux, we observe, on the 
southern slope of the mountain of Echanda, a line of demarkation, straight 
as if drawn by a cord, between the zone of shrubs and that of the short 
grass of the pasturages ; this is because the lower part of the Echanda is 
sheltered by a promontory above which the cold wind descending from 
the glaciers passes freely. On the sides of the volcano of Riiiihue, in 
Chili, M. Frick has remarked also that the line indicating the limit of the 
trees is perfectly horizontal.* 

The phenomena which contribute, each in its way, to render undecided 
the limits of the superposed floras vary in their action according to the 
innumerable diversities which the slopes present. E^^ory difference in the 
slope, the exposure, the nature, or the hardness of the soil, produces a cor- 
responding difference in the width of the zone, where the plant is freely 
developed. In one valley well sheltered from the cold winds, open to the 
warm breeze from the plain, and abundantly watered by rains, the plants 
of lower countries often ascend to heights several hundreds or even thou- 
sands of yards above their native soil ; in other places, on the contrary, 
the plants of the elevated zone, favored by the cold winds which are in- 
gulfed in the gorges, descend to a great depth below the imaginary limit 
of their abode. In the same way species which live in the neighborhood 
of the snows sometimes advance, with erratic blocks, on the surface %f the 
glaciers, and then are driven, with their terminal moraine, as far as the 
lower plains : at other times they fall from the top of the mountains with 
fragments of stone, and in passing at the foot of an escarpment we are 
suddenly surprised to see a foreign colony growing and thriving in the 
midst of plants of another climate. Even the avalanches of snow which 
slowly melt in the meadows beneath the passes from which they have 
fallen leave traces of particular species as signs of their sojourn there. 
Two laws act in contrary directions on the sides of mountains — one, which 
tends to cause the lower plants to ascend toward the summits, and the 
other, which tends to make those of the high peaks descend, and, in con- 
sequence of this incessant conflict, the limits of the zones are constantly 
displaced with the oscillation of the climates.f 

Since the time of Humboldt, Chimborazo and Popocatepetl have often 
been taken as types of mountains with superposed stages of vegetation ; 
still, these two mountains can not be cited but as representatives of the 

* Mittheilungen von Petermann,\864:, ii., p. 52. 

t E. Kambert, Les Plantes Alpines; Gustav Mann, Mittheilungen von Petermann, i., 1865, 



MINOLING OF THE FLORAS. 



381 



temperate regions in which they stand, for they are erected upon pla- 
teaux, and, in order to find a tropical flora, we must go to a great distance 
fi'om their bases. The Orizaba of Mexico, whose regular cone is so well 
seen from the sea, and tlie Sierra Nevada of Sta. Maitha, which towers 
19,500 feet above the shores of New Granada, are the most striking ex- 
amples of this arrangement of climates and floras in stages ; for from the 
base we may vaguely distinguish on the slopes a resume of the vegeta- 
tion of the globe, from the cocoa-nut palms which bend over the shore, to 
the Alpine plants, the verdure of which is recognized from a distance by 
the contrast it forms with the whiteness of the snows. On the sides of 
the volcano of Chiriqui, a mountain of less height, which also stands on 
the shores of the sea of the Antilles, M. Moritz Wagner was able precisely 
to measure the height of the successive stages. That of the palm-trees 
and the MusacecB rises to about 2000 feet ; the tree-ferns and orchids show 
themselves from 2000 to 4000 feet; above them the rosaceous family 
grows to 500.0 feet; and higher still, from 5000 to 10,000 feet extends the 
region of oaks and birches. In the island of Java, the isolated volcanoes 
which rise above the plains of exuberant tropical vegetation are also ad- 
mirably situated for enabling one to study on their sides the natural and 
cultivated floras, and the crops in their different stages, from the base to 
the summit of the mountains. 




FlarM tropical 

Plants of' ityjuns cold . 

J 



joS 



io8 



Fig. 169.— Botanical Map of Java. 

Isolated mountains which are bathed in an atmosphere where the me- 
teorological phenomena occur with great regularity, present, in conse- 
quence, a normal series of floras in stages from their summit to their base. 
Among the mountains which may be considered as types of the regular 
distribution of the zones of vegetation, we may cite* the peak of Teyde, 
the central mountain of the group of the Canaries. On descending the 
height of this volcano in the direction of Orotava, we at first see nothing 
but retamas — always retamas — a kind of grayish genista, which delights 
in a soil of ashes and cinders. All at once a new plant appears — a heath 
— and soon we are surrounded with heaths on all sides, and the retamas 
have completely disappeared. One solitary old pine marks the clearly- 



382 



LIFE. 



defined line of demarkation, which separates on the mountain side the 
zone of plants of sombre tints from that of verdant plants. In proportion 
as we descend, the heaths are higher and more crowded together; then 
they are mixed with ferns: toward 3800 feet of altitude the laurels rise 




Fig. 170.— Stages of Vegetation on the Planks of the Pic de Teyde, Isle of Teneriffe. 

here and there in the middle of the thicker brush-wood, and the volcanic 
soil is covered with grass. Below 3300 feet the crops begin — lupins, corn, 
and a few vegetables — while nettles are seen to grow at the edge of the 
path. At 2500 feet the first fig-tree is found, and then we enter the re- 
gion of vines, cactuses, and fruit-trees; finally, at 1000 feet we enter the 
sub-tropical zone indicated by the bananas and dracsenas.* 



too 



% 












<=^ 



tt; ^^ t; 



clASl 



?z. "iE-yB?!;—-.—.-:- :::;■— :: 

_-^--^ -_t'-§5^.^-(ka33rr..:^- 

I !. e-536u.. — 

-fLifea 



'~'>^ 



^~>K;;n. 



a EJuxiocLerLdron^ 

hUnc 

AFh- 



e Barley SyPotatoiS 

tOiestnuts 
yine/ 
k Limityof'Oie'OU;D&' 



Pig. 171.— Stages of Vegetation on the Flanks of Canigou. 

Among the high mountains of France the Canigou is that which rises 
most proudly above the plain, and on its sides, which are entirely visible 
from the open sea, M. Aime Massot and other botanists have been able to 
* Piazzi, Smith, Teneriffe, p. 266, and following. 



UPWARD LIMITS OF PLANTS. 383 

measure with great exactitude the separate zones of vegetation. The 
olive-trees, which cover the plains of the Tet and Tech, grow also on the 
oftshoots of the mountain at a height of 1300 feet; the vine rises higher, 
but at 1800 feet it disappears in its turn; above 2500 feet the chestnut 
ceases to grow. The last fields cultivated are rye and potatoes, which do 
not pass 3300 feet — a height at which the beech, the pine, the fir, and the 
birch already suffer from the wind and the cold of winter. The fir stops 
at 6400 feet, the birch does not venture beyond 6500 feet, but the hardier 
pine scales the rocks to the altitude of VOOO feet, not far from the summit. 
Above this the vegetation is only composed of Alpine or polar species. 
The rhododendron, the first tufts of which showed themselves at 4000 
feet, extends to a height of 8000 feet. As to the juniper, it climbs up the 
mountain, half hiding its branches in the soil to the terminal point 1000 
feet high, which is covered with snow during three months of the year. 

The stages of vegetation have been studied with care on the slopes of 
many other mountains of temperate Europe, especially on the sides of the 
Ventoux, by M. Charles Mai'tins ; but it is in the Alps, above all, that the 
most celebrated botanists of our century have made their comparative re- 
searches on the floras of the various altitudes. The limits of these floras 
vary, so far as we can understand, according to the form, exposure, and 
height of the mountains, the nature of the rocks, the moisture of the soil, 
the abundance of snow, and the meteorological conditions of the surround- 
ing atmosphere. It is, therefore, impossible to give the precise figures on 
the whole of the Alpine masses, and the averages obtained by savants 
have only a very general "value. Without taking account of the upper 
limit of cultivation, which varies singularly in the high valleys in propor- 
tion to the industry, intelligence, and social condition of the inhabitants, 
we may say that the vegetation of the plain hardly exceeds 3000 feet ; 
above this height, the slopes where man has not violently 'interfered to 
change the productions of the soil are naturally covered with vast forests. 
Still, the great trees gradually diminish in height in proportion as we rise 
into a zone where the air is rarer and colder ; their wood becomes harder 
and more knotted ; and the hardy kinds, which venture not far from the 
region of the snows, end by creeping on the ground, as if to seek shelter 
between the stones. To the north of Switzerland, the beech does not ex- 
ceed the height of 4000 feet, and the spruce fir stops at 6000 feet. In the 
group of Monte Rosa, the same forest growth, which approaches most 
nearly to the zone of perpetual snow, ascends as far as 6200 feet on the 
northern slope; while on the opposite side, the larch, still hardier, attains 
its upper limit at 7200 feet. Higher still, we only see the fantastically 
twisted trunks of a few mugho pines, rhododendrons, willow-herbs, and 
juniper-trees ; then all vegetation becomes more stunted, and is attached 
to the ground in order to escape the icy winds, and to allow of its being 
covered in winter with a protecting layer of snow up to the very edges 
of the glaciers and the white surface of the snows ; the phanerogamous 
plants will grow even at 11,500 feet high; we see androsaces, gentians, 



384 



LIFE. 



saxifrages, and the charming thrift, with its pink flowers gracefully placed 
on a cushion of green moss ; in the middle of summer, freshly fallen flakes 
will sometimes half cover these tiny plants, when we might think the 
snow was veined with blood. Even the highest rocks are covered here 
and there with lichens resembling rust, and often the very snows them- 
selves are shaded in red, green, or dull yellow, by a flora of rudimentary 
cryptogams. 



■Soi if Birch " ' '^ 





Fig. 172.— Stages of Vegetation on Sulitjelma. 

The distribution of the vegetable species is efifected in an analogous 
manner on the sides of other mountain chains, situated to the north of 
the Alps, the Vosges, the Erzgebirge, the Sudetes, and the Kjolen Mount- 
ains ; only as we can see on the slopes of Sulitjelma, which rises in Nor- 
way under the sixty-eighth degree of latitude, the series of stages of veg- 
etation become less and less rich in proportion as we advance toward the 
north, because of the gradual diminution of the mean temperature, and 
the relatively inconsiderable height to that at which perpetual snow be- 
gins. It is to be remarked, also, that the different species are far from 
succeeding each other in the same order on the slope of the mountains. 
The upper limits of plants present the most striking irregularities in this 
respect, and intersect each other variously instead of remaining parallel to 
one another, as we might expect at first. Thus the aspen rises to a less 
height than the beech in the Bavarian Alps, and the contrary occurs on 
the sides of the Canigou ; on the other hand, on this same mountain, the 
aspen leaves the hazel-nut far behind ; while in Bavaria it is distanced by 
it by about two hundred and twenty-five feet. We have attempted to 
make these remarkable phenomena more intelligible by means of a dia- 
gram. 

The polar limits of the various vegetable species do not succeed each 
other exactly in the same order, any more than the upper limits of similar 
plants on the slopes of mountains. These diff'erences in the distribution 
of corresponding floras are connected with the multitude of causes which 
hinder the propagation of plants over a more extended area. A plant 



DISTRIBUTION OF PLANTS. * . 335 

may be arrested on one side by the cold of winter ; on another, by fogs, 
drought, moisture, or the neighborhood of snows. Each region of the 
world having its special climate, also presents special conditions for the 
development of life. Even on the oj^i^osite slopes of a single mountain 
the stages of vegetation present remarkable contrasts. Thus the mount- 
ain-pine {Pinus uncinata) rises nearly six hundred feet higher on the 
southern slopes of Mount Ventoux than on the opposite side. On the 
other hand, the evergreen oak mounts to nearly 2000 feet on the northern 
side, and only to 1800 on the side fully exposed to the midday sun. We 



pk Aspen"""] 
^ C«r£antaA___ 



Fig. it:;.— Comparative Height of different Species of Plants ou Cauigou and in tlie Bavarian Alps. 

observe, too, that each declivity has its special growths ; to the south, it is 
the olive-tree; to the north, the walnut and firs.* In the Alps of Monte 
Viso and the Col de Tende it is seldom that we fail to observe a rhyth- 
mical alternation between the forests on sides differently exposed: larch- 
es cover the escai'pinents turned toward the south, while firs prefer shady 
valleys looking toward the north. On the mountains of the tropical zone 
the contrast is more striking still, since on one side impenetrable forests 
extend, and the other side has only herbaceous plants for its vegetation. 
Humboldt observed this contrast on the sides of the Duida, which com- 
mands the bifurcation of the Orinoco, and it can also be confirmed on 
most of the mountains of the Sierra Nevada of Santa Martha. 
* Charles Martins, Du Spitzberg au Sahara, p. 418, and following. 
^ 25 




386 ** LIFE. 



CHAPTER VI. 

UNCONITECTED SPECIES. — DISPLACEMENT OP AREAS IN CONSEQUENCE OF 
GEOLOGICAL CHANGES. — PLANTS OF GREAT BRITAIN. NATURALIZATION. 

* — INCESSANT MODIFICATION OF FLORAS. 

One of the most interesting phenomena of the terrestrial flora is the 
co-existence of the same plants in two regions separated from each other 
by vast spaces, where the transport of seeds would not have been possi- 
ble if nature had not employed other means than those which she em- 
ploys in the present period. It is certainly diiScult, in the present state 
of science, to render an exact account of this division of the areas of plants, 
but one can not study it too carefully, or give too great importance to it; 
for besides the stratified rocks and fossils, the flowers which spread over 
the ground recount in their silent language the history of past ages. 

Gmelin, and since his time a number of other botanists, ascertained that 
the vegetation of the mountains of Switzerland does not only resemble the 
flora of polar regions by the general physiognomy of its plants, but that 
it also comprehends species perfectly identical with the plants of Spitz- 
bergen, Greenland, and Arctic America. On the terminal cone of the 
Faulhorn, M. Charles Martins has gathered one hundred and thirty-two 
phanerogams, forty of which are found again in Lapland, and eight in 
Spitzbergen. In the same way the " Jardin," which stands isolated in the 
midst of the glacier of Talefre, resembles, by its scanty flora, a polar coun- 
try much more than a rock among mountains of the temperate zone. In 
this little ice-girt world, which botanists have lovingly studied to the very 
farthest corner, one hundred and twenty-eight species of plants live, but 
only eighty-seven phanerogams ; of this number, fifty belopg also to the 
Faulhorn, twenty-four to Lapland, and five to Spitzbergen. Observations 
made on other elevated points of the Alps, at the Grands Mulcts, and in 
the pass of St. Theodule, have given analogous results. On the White 
Mountains of New Hampshire we also find the same species as those of 
Labrador, many of which belong equally to the mountain flora of the Alps 
and the Pyrenees. Finally, the Atlas and Abyssinian mountains, the peak 
of the Cameroons, the volcanoes of Java, the chains of Brazil and the 
Andes, and even the rocky escarpments of Terra del Fuego, have among 
their species some European plants. Enormous distances — from 600 to 
6000 miles — separate these divided areas of mountains to the south and 
plains to the north, and we can not believe that birds or atmospheric cur- 
rents could have carried the species from one region to the other, for the 
naturalization of species is most difficult in cold countries ; and most of 
these far-scattered plants have neither berries such as the birds seek for, 
nor winged seeds such as are carried by the wind. 



EFFECTS OF OEOLOOICAL CHANGES. 38V 

The same difficulties present themselves when it is necessary to explain 
how a great number of fresh-water species live in rivers and lakes, de- 
prived of all communication with one another. These are plants whose 
heavy seeds can not be transported by the air, and which the sea-water 
would destroy in time ; nevertheless, these plants have been able to pen- 
etrate into almost all lacustrine and fluviatile basins, where the tempera- 
ture suits them. They are seen in islands as well as in continents ; they 
grow on both sides of wide seas, and in the waters which bathe the op- 
posite flanks of high mountain chains ; and, by a remarkable coincidence, 
it is precisely these aquatic species, with necessarily limited requirements, 
which are found most frequently alike in the different countries of the 
earth. Respecting these water plants, just as regarding those of the 
mountains, botanists ask how they have been able to establish themselves 
at the same time in the cold or temperate regions of the two hemispheres 
at the opposite extremities of continents, since the torrid zone, which sep- 
arates the areas of habitation by a distance of several thousands of miles, 
forms an insurmountable barrier between them. Thus even at the two 
antipodes, in New Zealand and in the seas of Western Europe, Hooker 
has recognized twenty-five identical species of algae. The genus Spartina 
presents the most singular contrasts in this respect. One species, Spar- 
tina stricta, grows in the United States, and in Europe on the shores of 
the Atlantic, and is found at Cayenne, at Venice, and at the Cape of Good 
Hope. Another species, the Altern.'iflora., found alike on the coasts of 
America, in the United States, and in Cayenne, only shows itself in France 
at one spot, the mouths of the Adour, and in England on the shores of 
Southampton. Finally, the species called Juncea, which flourishes in 
Georgia and in Massachusetts, only appears in the Old World at Frejus, 
near the embouchure of the Argens. 

It is true that these last-named plants, living always in the sand and 
alluvial lauds of the sea-coast, might easily have been transported by ves- 
sels with the ballast and merchandise from one shore of the ocean to the 
other, and have propagated themselves after having remained for a time 
in sea-water. M. Godron has seen the seeds of grasses germinate after 
immersion during a winter in a salt pool. Darwin and Martins have also 
proved by direct experiments that certain seeds can preserve their power 
of germination after having floated on the sea during twenty-eight and 
even one hundred and thirty-seven days. They think that a tenth of the 
plants can thus propagate themselves spontaneously along the shores.* 
Perhaps even the Eriocaulon septajigtdare, an American fresh-water plant, 
which flourishes also on the Scotch island of Skye and the Irish district 
of Connemara, has been carried from Canada by the Gulf Stream. It is 
known what a marvelous vitality certain seeds possess. Robert Brown 
caused the seeds of Nelumhiuin speciosiim, deposited in an herbarium for 
one hundred and fifty years, to germinate. Perhaps, too, the various seeds 
contained in the Egyptian tombs could, as many botanists assert, have 

* Origin of Species, p. 365. 



388 LIFE. 

preserved their latent life for thirty and forty centuries. Many geolo- 
gists, indeed, believe that the rare plants suddenly springing up above 
the remains of ancient fossiliferous strata originate really from seeds that 
have been buried during a whole series of terrestrial revolutions.* 

However it may be, such phenomena occur in too small a number of 
plants for us to be able to explain in this way how so many vegetable 
species having several habitats can flourish at a distance from the sea and 
all highways of commerce, either in lakes and streams, or on the sides of 
snowy mountains. We can only imagine two alternatives in the case of 
these plants — either their germs have been developed spontaneously on 
all the spots where the separate colonies are now found, and each mount- 
ain summit, each fluvial and lacustrine basin has become an independent 
centre of vegetable generation ; or else the snow-scattered colonies were 
formerly connected ^\%\i one another, and have been gradually separated, 
or even displaced, in consequence of the changes of the surface or cli- 
mates of the earth. The humble Alpine flowers, hiding in the snows and 
in the crevices of rocks, would thus relate the great revolutions of the 
globe. 

In fact, during the earlier geological periods the mean temperature 
underwent frequent changes, as the fossils in the strata of the earth 
prove. In the same country the climate has been alternately hot, tem- 
perate, and cold ; then it has become heated again, and consequently the 
living organisms, plants and animals, have been incessantly displaced on 
the surface of the earth.f Toward the end of the tertiary epoch, when 
the regions which have now become the continents of Europe and North 
America still enjoyed a high temperature, the vegetation must have had 
a much more southerly chai-acter, on the whole, than in our days : in the 
same way the scattered lands which surround the Arctic pole had doubt- 
less a uniform flora, composed of plants analogous to those of our temper- 
ate zone. But the climate gradually changed, and the cold which was to 
bring on the glacial period began to reign over the northern hemisphere. 
There was a repulse of the species which had advanced too far toward the 
north and missed the necessary warmth. They beat a retreat before the 
snow and ice like an army in flight. The plants of the polar zone gained 
little by little on the temperate zone, those of t"he temperate zone retreat- 
ed toward the tropics, and, by the gradual encroachments of their colo- 
nies, even crossed the equator and established themselves on the now- 
scorching plateaux and plains of the torrid zone. During the series of 
centuries of an unknown length which elapsed during the glacial epoch 
of our planet, a certain number of displaced species sought vainly to ac- 
commodate themselves in their new countries, and ended by succumbing ; 
while other plants, favored by the climatal conditions, grew without diffi- 
culty in the land of their exile, or even enjoyed greater prosperity there 
than in their ancient abodes. 

* Alph. de Candolle, GSograpkie Botanique, p. 1067. 
t See The Earth, the section entitled The First Ages. 



MODIFICATIONS OF CLIMATE. 339 

Nevertheless, the temperature, changing incessantly like all the phe- 
nomena of the universe, entered upon a new phase : to the cold period 
succeeded an increasing warmth on the surface of the northern hemi- 
sphere, and perhaps over the whole earth. The glaciers which filled all 
the mountain gorges and advanced far into the plains, retreated gradual- 
ly toward the peaks, leaving in the fields heaps of the earth and debris 
which they had carried for centuries. To the north, the snows of conti- 
nents and the ice-fields of the sea retreated more and more from the tem- 
perate zones, and approached nearer to the poles. Owing to the warmth, 
plants which the cold had forced to take refuge in the equatorial regions, 
and had enabled to propagate themselves in both hemispheres, were thus 
divided into two distinct cor2)s d'armee, retiring from each other in pro- 
portion as the temperature increased. In the same way, the species of the 
temperate zone gradually encroached on the ground in the direction of 
the pole, and, advancing to the assault of the mountains, took possession 
of the moraines and ravines abandoned by the glaciers; but in order to 
conquer the mountains and polar regions, they were obliged to yield the 
intermediate plains to other plants which had come from the south. An 
ever-widening space, occupied by a new flora, interposed itself between 
the two separated fragments of the ancient flora, and in our days, after 
the lapse of ages, the European species of the glacial epoch have no long- 
er any other country than the Arctic lands, and the rocks surrounded by 
snow on the summits of the Alps and Pyrenees. Like those tribes of 
mountaineers, Basques, Romanches, and Vaudois, who, to preserve their 
customs and their nationality, have taken refuge in high valleys, the lit- 
tle vegetable population, besieged by the plants of the lower plains, have 
retired to the snowy heights, where they find a climate which reminds 
them of the glacial epoch. Thus all distributions of species which can 
not be explained by the present condition of the terrestrial surface may 
be explained by reference to former conditions. 

This is not all : to such important alternations of climate are added also, 
for the modification of vegetable areas, the numerous changes of form and 
relief to which the continents have been subjected. When Scandinavia 
was an insulated country, when a vast sea occupied a great part of the 
plains of Northern Germany and Russia, and a strait allowed the Black 
Sea, the Caspian, and the Gulf of Obi to communicate with each other, 
there is no doubt that maritime currents and convoys of floating ice 
served to transport Arctic species to the sides of European mountains. 
Later, while the countries of Europe rising out of the Scandinavian sea 
gradually assumed the contours that they have now, their relief was also 
modified in various ways ; the heights were elevated, and thus separated 
basins formerly united ; hills worn awaj by the waters disappeared little 
by little, and in their destruction a communication was opened between 
two valleys formerly distinct ; lakes were formed, others were dried up, 
and rivers changed their courses. Thus the soil, with the seeds which for- 
mer vegetations had deposited there, was incessantly altered. Why, there- 



390 LIFE. 

fore, should we be astonished to see the same aquatic plants flourish in so 
many basins now completely isolated ? Communication which does not 
exist now existed, directly or indirectly, during previous geological ages, 
and that is sufficient to explain the co-existence of scattered areas of hab- 
itation. However, in following this path, it is so easy to allow one's self 
to be carried away by daring suppositions, that it is important to prove 
established facts very carefully before adopting them. Thus M. Schmidt, 
having ascertained that the present flora of the coasts of Siberia and 
China resembles much more that of the Atlantic shores of the United 
States than that of California and Oregon, concludes from it that Asia 
and America formerly composed a single continental mass, and then that 
a part of the centre, after having been gradually submerged in the depths 
of the Pacific, rose again, to re-clothe itself with a second flora entirely 
different from the first.* 

The flora of the British Isles is a remarkable example of the changes 
which have operated during the modern period in the areas of species. 
With the exception of a single plant of American origin, the M-iocaulon 
septangulare, which is found in a part of the Hebrides,! ^^^ whole Anglo- 
Irish vegetation is of continental origin. The great majority of the spe- 
cies have been propagated directly from France, Holland, and Germany, 
before the English Channel had been opened by the waves. Another 
flora in the north of quite an arctic character must have been brought 
from Scandinavia by icebergs laden with debris ; finally, the arbutus, and 
about ten of the plants growing in the mountainous regions of the south- 
west of Ireland, are only found again on the shores of the Gulf of Gas- 
cony, in Portugal, in Madeira, and the Azores ; and there are strong rea- 
sons for admitting, with Edward Forbes, that they formed part of the flora 
of a great continent which has now almost wholly disappeared. Thus the 
modifications of climate and the oscillations of the soil, without counting 
the still more important changes introduced by the work of man, have re- 
sulted in concentrating parts of three very distinct floras in the relatively 
narrow space of the British Isles. Besides this, eighty-three species of 
foreign origin have been naturalized there during modern centuries by 
the voluntary or involuntary intervention of man, who is himself one of 
the great geological forces. 

Since the discovery of the New World, the two continents, which navi- 
gation continually joins together, have mutually enriched their floras by 
the naturalization of new species. At least thirty-five plants of North 
America have acclimatized themselves in Europe, and one hundred and 
seventy-two European species have been propagated on the soil of the 
United States. America has thus greatly gained in this exchange. Eu- 
rope has discharged on the New ^orld vegetable populations as well as 
human populations; and these colonizing plants, invaders like the rude 
pioneers themselves, have in many spots displaced the native species. In 

* Compte Rendu de la Societe Geographique de Russie, p. 21, 1864. 
t See above, p. 387. 



NATURALIZATION OF SPECIES. 39 1 

less than a; century it is said that the common trefoil of Europe has con- 
quered nearly half the continent from Louisiana to the Rocky Mountains. 
In Australia, Van Diemen's Land, and New Zealand, the invasion of the 
conquering plants is accomplished in perhaps a more rapid manner still ; 
a few years sufficed to change the physiognomy of the vegetation in 
whole distj'icts. The European colonists, occupied only with agriculture 
and commerce, would willingly leave to their new country the strange 
flora whose very aspect astonishes them ; but from their fields and gar- 
dens plants which have come with them from Great Britain escape, and, 
spreading, take possession of new domains ; more rapid in their triumph 
than the English themselves, they are incessantly driving before them 
the aboriginal plants. The ancient flora, scarcely modified since distant 
geological epochs, is greatly changed in less than a century; one might 
say that these countries, the last representatives of a vanished period, 
abandon the fashions of the old times to dress themselves in new cos- 
tumes. Thus the conquering peoples and the colonists are always ac- 
companied by species of plants, invaders like themselves. The Persians 
and the Greeks, the Crusaders, the Arabs, the Mongols, and the Russians 
have carried the plants of their country with them in their wars of inva- 
sion, in the same way as English and American pioneers carry theirs into 
the solitudes of uncultivated lands. In this point of view, the history of 
the plants which have been naturalized without the knowledge of man is 
to some extent connected with the history of humanity itself 

If there are botanical areas which increase in extent, there are, on the 
other hand, many others which are gradually restricted, or which even 
disappear : certain plants have not only been driven back like the Maoris 
of New Zealand, or the Redskins of North America; they have been 
completely destroyed, and no longer exist except in herbariums, or else 
in the state of dormant seeds in the crevices of rocks. Thus Darwin tells 
us that during a century the island of St. Helena has lost a great number 
of species. Its flora, composed of 746 phanerogams, almost all of English 
importation, no longer comprehends more than fifty-two indigenous spe- 
cies : its ancient forests of difierent species, which extended over more 
than 1900 acres, have entirely disappeared, and several species have been 
utterly annihilated by goats and pigs; others are dangerously threatened, 
and botanists expect soon to have only the recollection of them. Even 
in Europe, where colonization has not suddenly changed agriculture and 
vegetation, plants have certainly ceased to grow in various countries. 
Thus the water-chestnut {Trapa 7iatans) and the dwarf water-lily, which 
peopled the waters of Switzerland at the epoch of the lake cities, are no 
longer to be found in that country. Certain regions of Ireland, where the 
forest vegetation has been completely destroyed, either by man or by natu- 
ral causes, still possess, under their incessantly increasing beds of peat-moss, 
fragments of pines and oaks ; in the same way in the Shetland Islands, 
trunks of a fir-tree {Abies pectmata), which is now completely wanting in 
the British Isles, and even in Scandinavia, have been found in the peat. 



392 LIF^- 

Besides, the experience of all the foresters and the testimony of history- 
are amply sufficient to demonstrate that nature requires a continual 
change, an incessant rotation in the products of the soil. In all coun- 
tries, if a forest be burned, it is immediately replaced by other species ; a 
"re-growth" of new trees springs from the earth instead of the old spe- 
cies — then, after a certain number of centuries, disappears in its turn, to 
give place to the trees of former times ; in the forests of Perche, each of 
these re-growths lasts, on an average, from 290 to 330 years. Even when 
fire or violent destruction does not suddenly sweep away a forest, the lat- 
ter does not the less transform itself in the course of centuries. Accord- 
ing to M. Paul Laurent, a forest of Europe that in the Middle Ages con- 
sisted of beeches is to-day composed of oaks. Similarly, forests of oak, 
like that of Gerardmer, where Charlemange went hunting, have been re- 
placed by the fir and pitch-pine ; the forest of Haguenau, now a pine- 
wood, was composed of beeches a century and a half ago. Finally, a 
number of localities which have formerly received the names of Char- 
mettes, Pinasse, or Piniere, Chataigneraie, Tremblaie, Boulaie, no longer 
have the species which have given them the name they bear. In the 
meadows, also, M. Dureau de la Malle says that a rotation lasting for 
several years is established between the graminaceous and leguminous 
plants. The vegetable populations are constantly changing; the life 
which germinates from the ground is, like the ground itself, in a state of 
perpetual transformation. 



ORIGIN OF LIFE. 393 



BOOK II.— THE LAND AND ITS FAUNA. 



CHAPTER VII. 

ORIGIN OP LIFE. — SPECIES OF ANIMALS. — MULTITUDE OP ORGANISMS. 

CONTRASTS OF LAND AND SEA. 

Naturalists have not yet distinguished precisely, amidst the multi- 
tude of incipient organisms, the boundary which separates the plant from 
the animal. How many dubious forms there are ! How many indefinite 
species, diificult to class in one or the other systems of organized beings ! 
Are they vegetables ? They grow and are developed like them. Should 
they be cla*ed among the animalculje? They move and devour then- 
prey. Placed, so to say, on the threshold of life, at the common origin of 
the innumerable generations which are born and die on the earth, they 
naturally appear to us as the ancestors of all the species, more and more 
developed, which succeed each other in parallel series up to the tree and 
the mammal. For it is in them that, perhaps unconsciously, that special 
activity arises which in the higher organisms manifests itself with such 
great energy. Besides, we do not know what life is in those primeval 
shades where the germs are elaborated, where matter is disengaged from 
the rock or from the ooze, to change into little separate worlds. It is 
only by the consciousness of his own life that man can judge of that of 
other species : he takes his place proudly apart, and yet it is by bringing 
all into relation with himself that he establishes the series of living crea- 
tures. 

The number of animals is probably not less than that of plants. The 
number of species is estimated provisionally at 260,000 or 280,000 ; bjit 
in reality it is unknown, excepting for the higher groups; and it is pre- 
cisely these groups whi'ch are less rich in animals of difierent forms. The 
first class, that of the mammalia, is also distinguished from all the others 
by the least considerable number of representatives. Scarcely 1400 can 
be counted on the entire surface of the planet, in the waters and on the 
dry land. According to M. Selys-Longchamp, there would be in Europe 
only 121 species of terrestrial quadrupeds, and in this relatively small to- 
tal it is the small-sized animals that form by far the greater number. In 
the same way, of the 8000 varieties of birds known to naturalists, more 
than 5000 are of a size not exceeding the sparrow. The insects, much 
smaller, on an average, than the animals of all the higher classes, com- 
prise in themselves alone more than 150,000 species — that is to say, about 
three-quarters of the whole fauna already studied by scientific men. And 



394 - LIFE. 

yet below the world of insects, crustaceans, raollusks, worms, and echino- 
derms, moves an immense swarm of animalculse, which are at once the 
admiration and the despair of those who seek to investigate them by aid 
of the microscope. The organs of these wonderful creatures escape our 
sight ; often even the drop of water in which they move, and which is 
their universe, is invisible to the naked eye ; but they compensate for their 
smallness by the variety of their forms. Man can certainly attempt, 
thanks to method and accumulated observations, to enumerate the infi- 
nitely small species; but the task is hardly begun, and it is pursued with 
difficulty beyond the world of visible insects in that obscurity where 
only the thought of the mathematician seeking to apprehend atoms has 
penetrated. At all events, that which we already know enables us to 
recognize, at least from the mammal to the insect, a law of progression 
according to which the species are more and more rare in proportion as 
they rise in the series of beings. In acquiring complication of structui'e, 
they lose in diversity of form ; they improve, and become, so to say, a re- 
sume of the inferior species, but at the same time they are more and more 
limited in number, as if nature required more strength to produce them. 
By a remarkable contrast, it is precisely the contrary that we observe in 
the vegetable world. There it seems that the numbers of species and 
individuals increase in proportion to their degree of development. The 
phanerogams have many more representatives than the cryptogams. 
The dicotyledons are more numerous than the monocotyledons, and in 
these two great divisions of plants with visible flowers, it is the highest 
families, the graminaceous and composite plants, which are also the rich- 
est,* 

If the multitude of species which constitute the whole of the earth's 
fauna does not yield in number to that of the flora, the host of individuals 
is equally innumerable ; nothing more numerous can be imagined than the 
herbs and vegetables of every sort which clothe the surface of the earth. 
It is true that, in consequence of their relative independence, animals are 
much less visible in nature, while vegetation forms a continuous carpet 
over the globe, and the green of the trees or the grass appears to us like 
the normal color of the surface of the earth ; animals, hidden under the 
verdure or in holes in the ground, seem at times to be completely absent 
from the landscape. On the other hand, the vegetables requiring a nour- 
ishing soil to support them, only spread over its surface, while a number 
of animals can, owing to the freedom of their movements, be accumulated 
in enoi'mous masses on the earth, or fly in clouds toward the sky, or else 
move in myriads in the depths of the sea. The atmosphere and the ocean, 
no less than the surface of the earth, are the domain of animal life; it is 
only by millions that one can estimate the number of the passenger-pigeons 
of the United States, whose bands, traversing the sky with a speed of fifty 
miles an hour, take three days in passing by ; it is by milliards that we 
estimate the grasshoppers which descend upon the provinces, and cover 
* Schleiden, Das Meer, p. 165. 



RELATIVE ABUNDANCE OF ANUfALS. 395 

them with blackish masses, glittering in the sun like a sort of cuirass, 
while they eat up all plants to the root. Finally, all calculation becomes 
impossible, and imagination itself is powerless, when we would speak of 
the clouds of gnats which darken the air above the marshes of Louisiana 
and Colombia, or over the grand lakes of North America, and particularly 
when we think of the innumerable organisms which swarm in the ocean. 
There is, therefore, an equilibrium, so to speak, between the two forces 
striving for the possession of the earth, between the flora and the fauna, 
the vegetable world and that which feeds on it. 

The poets of former times, according to Homer, were pleased to give 
to the sea the epithet of " barren," and yet nothing equals its exuberant 
fecundity. Much more than the earth, of which the surface is only rich- 
ly peopled, the ocean is the domain of life. Not only its upper sheets, 
but also the deeper strata, are filled with organisms of every kind; in 
certain parts, the myriads, and myriads of creatures are crowded in such 
prodigious multitudes that the waters themselves, so to say, are alive. 
There may, perhaps, be found in the vast watery tracts some deserts al- 
most entirely destitute of life ;* but these are exceptions, and in most of 
the regions of the sea every drop of water is a world from the multitude 
of l&eings that inhabit it. Taken as a whole, the ocean may even be con- 
sidered the special centre of life. It is in the waters, swarming with ani- 
malculse, that continents are gradually formed by the deposit of organic 
remains. New generations, unceasingly at work, lay the foundations of 
future continents. It is in the sea, too, as palaeontologists tell us, that 
the primitive species must have originated from which all the present 
forms, oceanic and terrestrial, are descended. The great basin of the 
seas is the cradle of life. " Water is the beginning of every thing," said 
Thales of Miletus 2500 years ago.f 

A long time ago Humboldt made the remark that the ocean is, in con- 
trast to the emerged lands, the principal centre of animal organisms, 
while the continents are in especial the domain of vegetable life. In 
fact, the waters of the sea often owe their color and phosphorescent 
brightness to the numberless animalcule which are developed there in 
prodigious quantities. Over immense extents, the bottom of the ocean, 
as discovered by the sounding-lead, is an animated ooze, each cubic inch 
of which contains millions of living creatures. The earth, on the other 
hand, excepting where in desert regions it is unprovided with water, is 
naturally covered with a carpet of verdure, plants, large trees, and in' 
numerable parasites. The forests of polypes, in the South Seas, the poly- 
thalamia, which fall like snow from the surface of the water to the bot- 
tom of the Atlantic, the banks of herrings and stromlings^ where the fish 
are as thick as the grass of the prairies, find their contrast in the seas of 
foliage, on the plains of the Amazon, in the undulating savannas which 
stretch beyond the sight, and even in the cultivated fields variegated 
with so many diff*erent plants. 

* Marcon, Les Rochers du Jura. t Schleiden, Das Meer, p. 124. 



396 LIFE. 



CHAPTER VIII. 

THE OCEANIC FAUNA. 

The contrast between the land and the seas manifests itself also in the 
respective dimensions of their forms of life. The ocean, so rich in in- 
finitely small organisms, numbers also among its animals monsters far 
larger than those of the dry lands, .while the greater part of its plants, 
and even those prodigious fuci several hundred yards in length, are noth- 
ing but simple strips, and present neither roots, trunks, nor branches 
which may be compared with the oak, the baobab, and the chestnut. As 
to the organization, it is of the most rudimentary kind. With the excep- 
tion of a single family of phanerogams, the mai'ine algaB are all of the 
lower orders of plants, without apparent fructification. The pelasgian 
plants have neither calyx, nor corolla, nor stamens, nor pistils. On the 
other hand, many animals are fashioned like flowers,* and the earliest 
naturalists were often deceived by them. For a long time the most 
learned among them, and even Reaumur himself, saw in these polypes 
real plants; and in our day many investigators have demanded if the 
algse were not also, like the branches of coral, a kind of structure of vege- 
table form built by innumerable social animalculae. In any case, it is cer- 
tain that the generating granules of algse move exactly like animalculae, 
and, as it seems, " by an act of their own will ;" they come and go, ad- 
vance toward the light, and only fix themselves after having found the 
place that suits them in which to build their cellules. This is one more 
proof that the division between the two series, vegetable and animal, is 
in great part artificial, f 

In their love of the marvelous, and perhaps also because of the terror 
which the sight of these monsters of the sea had occasioned them, our 
ancestors gave to these gigantic animals a size out of all proportion with 
their real dimensions. Numerous ai'e the legends which speak of whales 
on which one could disembark as on islands, but which then plunged sud- 
denly, and left their visitors fighting with the waves. The seamen of all 
nations recount also a host of stories about monstrous serpents which 
unrolled their rings over several large successive waves, and of polypes 
whose arms, incessantly in motion, resembled a forest agitated by tem- 
pests. The observations made by naturalists do not confirm these tales ; 
but it is certain that whales have been measured more than 100 feet long 
and 65 feet in circumference, weighing nearly 200 tons — that is to say, 
more than an army of 3000 men. Scoresby saw a rorqual more enor- 
mous still, which was no less than 120 feet from head to tail. As to 

* Schleiden, la Plante. 

t Unger, de Mirbel, Paul Laurent, Payen.— Maugin, Mysteres de V Ocean. 



FECUNDITY OF TEE OCEAN. 397 

monsters of the size of the hippopotamus or the elej)hant, such as dol- 
phins, orcas, cachalots, walruses, and sharks, the species are very numer- 
ous; and we often meet wHh individuals of this dimension in groups of 
hundreds and thousands in a limited space. Among the marine animals 
of an inferior order, such as cephalopods, there are some also of a pro- 
digious size ; thus specimens of the Gyanea arctica have been fished out 
of the Bay of Massachusetts 6^ feet in thickness, and the arms of which 
were not less than 114 feet long.* And certainly it may be asserted be- 
forehand that the ocean still keeps in reserve many surprises for natural- 
ists who will explore all its abysses. 

Still,, if the sea may be considered as the principal theatre of animal 
life, it is not so much because of the size and strength of its monsters as 
by the prodigious multitude of creatures which are agglomerated in rows, 
heaped up in banks, and swarm in immense beds. It is easy to imagine 
what innumerable armies offish must fill the ocean, since a single female 
may lay a hundred thousand, or million, or even more than ten millions 
of eggs. In the second generation, a single couple of these fish may have 
given birth to a hundred trillions of individuals ; in the third generation, 
the entire sea, with its unfathomable abysses, would be filled with a com- 
pact mass of fish. But even before they are born, this numberless prog- 
eny is pursued by equally numerous enemies. The sea is an immense 
field of carnage, where the creatures which are born in infinite myriads 
serve also as food to millions and tens of millions of furious devourers. 
When the herrings penetrate into the North Sea, " it seems as if an im- 
mense island had risen, and that a continent was about to emerge ;"f but 
this island or continent of fishes is beset and eaten on all sides. Each 
detachment of the mighty army, about thirty miles long and from five to 
six broad, is accompanied by legions of cetacea and other great sea ani- 
mals, which press in bands around the serried columns, and never cease 
swallowing herrings by hundreds ; birds flying in clouds above the scene 
of the immense slaughter plunge down on all sides to select their victims; 
an oily substance resulting from the thousands of torn fish floats on the 
surface of the sea. J When at last the fishermen, warned of the approach 
of the bank of herrings, rush to their capture, the massacre assumes the 
most frightful proportions. The fishermen of the single district of the 
Goteburg kill as many as a hundred and fifty millions of herrings in a 
single campaign ; those of Bergen three hundred millions ; those of Yar- 
mouth even more. The number of herrings captured during the fishery 
by the seamen of Northern Europe must be estimated at tens of millions. 

There are certain parts of the ocean where the fish are still more nu- 
merous than on the coasts of Western Europe ; such is, for example, the 
Bank of Newfoundland, where, in consequence of the meeting of two mar- 
itime currents, difiering in temperature and the fragments they bring, all 
the conditions favorable to the development of a great diversity of species 

* Elizabeth and Alexander Agassiz, Sea-side Studies. 

t Miehelet, la Mer. X Alfred Fredol, le Monde de la Mer. 



398 LIFE. 

are found united. It is in the neighboring seas that the Esquimaux, whose 
name signifies "eater of raw fish," finds his food in abundance ; it is there 
that the fishermen — English, French, and American — go each year to seek 
their provisions from the two or three millions of codfish left by the mul- 
titudes of cetacese that are always at work. In the North Pacific, on the 
shores of Japan, round the Canaries, are other fisheries scarcely less rich, 
whence the net is sure to bring each time numerous victims. 

As to the marine animals other than fish, a number of species swarm in 
masses all the more compact the smaller the individuals themselves are, 
From the heights of the promontories which rise in peaks above the gulfs 
of New Granada to the east of Santa Martha, the sea is sometimes seen as 
far as the horizon filled with yellow medusae, so crowded one agamst the 
other that the color of the waters is quite changed by them. A swarm 
of medusae, through the midst of which Piazzi Smyth passed in July, 1856, 
to the north of the Canaries, occupied a space about forty-five miles wide, 
and comprehended in the superficial bed alone two hundred and twenty- 
five millions of individuals. Whales and other cetaceae devoured enor- 
mous quantities of these graceful orange-veined medusae, and, on their 
side, each of these animals absorbed myriads of siliceous diatoms. The 
quantity of these inferior organisms contained in the stomach of each me- 
dusa amounts certainly to seven hundred thousand ; it is therefore by 
tens of thousands and by millions that we must estimate the creatures 
swarming in each wave.* Sailors, accustomed to see the innumerable 
multitudes of medusae, only see in them " the scum of the sea ;" and Bacon 
himself, that great observer, thought that the marine jelly-fish were noth- 
ing else than "heated foam." More poetically, the Peruvians-of the coast 
of Iquique give to one of these animals the elegant name of Aqua viva,\ 
or " living water." 

Sometimes the sea is so filled with living organisms that one might call 
it saturated, and its color is entirely changed by the floating multitudes. 
Thus on the coasts of Greenland seamen traverse broad bands of a deep 
brown or olive-green color, being frequently one hundred and eighty and 
even two hundred and fifty miles long ; they are banks of medusae, every 
cubic inch of water containing hundreds, and swallowed by hundreds of 
thousands in every mouthful of a whale. Elsewhere navigators observe 
immense " sea-serpents," formed by innumerable salpas, which are attached 
to one another like the particles of one and the same body, or else they 
form expanses without visible limits, some red as blood, others white as 
milk. There they are not banks, but worlds of animals, where each drop 
contains as many as there are stars in the milky way. In August, 1854, 
Captain Kingman traversed in the Indian Ocean a space more than twen- 
ty-five miles wide, the whiteness of which was dazzling enough to extin- 
guish the light of the stars ; and when the sea of animalculae was passed, 
the sky above it was for a long time seen to shine as with the light of a 
feeble aurora borealis. Ten years later, the vessel La Sarthe found again 
* Piazzi Smyth, Tener'iffe, pp. 5, 6. t Bollaert, Antiquities, p. 256. 



MICROSCOPIC ORGANISMS IN THE SEA. 



399 



in the same part a vast " sea of ibilk," where the furrow of its prow made 
a black line. 

Is not, however, the marvelous phosphorescence of the waters, due in 
great part to living animalcula?, the most astonishing testimony to the in- 
numerable host of organisms which swarm in the ocean ? There is no 
voyager who has not observed during the night those sheets of yellow or 
greenish light which tremble on the sea, those sheaves of lightning which 
spring from the crests of the waves, those whirlpools of sparks which the 
prow of the vessel causes in its plunge, those waves of flame which glide 
from either side of the ship to unite in long eddies behind the rudder, and 
transform the track into a river of fire. In the port of Havana the least 
object which agitates the surface of the water appears suddenly like a 
line of flame, and raises around iU a whole series of luminous wavelets, 
propagating themselves in concentric circles to several yards in distance. 




Fig. 174.— Organisms from the Sea-bottom. 



Boats sailing over these waters, driven by the equal movement of the 
oars, leave behind them the trace of an immense fiery dragon, with large 
paws extended. In the Persian Gulf, Palgrave tells us that the. waves 
are so luminous during the night that the Arabs attribute these reflec- 



400 LIFE. 

tions to the infernal fires shining througlfthe rocks beneath the transpar- 
ent mass of waters.* Modern science explains to us the phenomena of 
the phosphorescence otherwise. According to the researches of Boyle, 
Forster, Tilesius, and Ehrenberg, this light results from innumerable ani- 
malculae, some living, and others in decomposition. 

The little organisms called foraminifera, because of the numerous holes 
in their shells, are probably the creatures which people the tracts of the 
ocean in the greatest multitudes ; the bottom of all the seas is, without 
exception, strewn with their thin calcareous shells, of which one drachm 
of sand contains sometimes nearly 16,000, according to a calculation of 
M. d'Orbigny. Among the various genera of this family, which compre- 
hends nearly 2000 known species, the globigerina, which has an ovoid or 
spherical shell, may be considered as tlfe special oceanic genus, since it is 
met with in all latitudes and at depths varying from 50 to 3000 fathoms. 
Their remains cover thousands of square miles of surface at the bottom 
of the ocean ; and when the lead brings up specimens of the ooze, it is 
often found that it is composed of 75, 80, or even 97 per cent, of the skel- 
etons of a single species of globigerina.f The rest of the sediment is 
formed of other debris of little animals, spicules of sponge, and star-fish. 
Besides these, there are the siliceous organisms, the diatoms, which aid 
in filling up the marine depths. But do these bodies of such a perfect 
regularity, disks and triangles, parallelograms, pyramids, and other geo- 
metrical figures, all so gracefully ornamented with the finest arabesques, 
belong to the vegetable world ? The botanist Schleiden believes so. Or 
are they rather animals? The zoologist Ehrenberg asserts it. But wheth- 
er they be plants or animals, they ai'e not the less one of the most impor- 
tant agents in the continuous formation of our globe. J 

* Journal of the Geographical Society, 1864. 

t Wallich, North Atlantic Sea- bed; Parker and Jones, Phil. Trans., vol. civ., part i., 
1865. 
t See below, p. 422. 



INFLUENCE OF CLIMATE. 401 



CHAPTER IX, 

INFLUENCE OF CLIMATE AND PHYSICAL CONDITIONS OP THE SPECIES OF 

ANIMALS. 

Animals, like plants, depend on all the conditions of climate ; heat and 
cold, light and darkness, dryness and moisture, influence them in various 
ways, and give them a clearly-delined area of habitation. Nevertheless, a 
great number of species possess an advantage over the plants ; for while 
these latter can not fly spontaneously before an ungenial climate, and the 
displacement of their race takes centuries in accomplishing, animals, en- 
dowed with locomotion, can more readily migrate to countries which offer 
a temperature suited to them. Hundreds of species of birds and fishes, 
numerous tribes of insects, migrate every year, and are thus able, owing 
to the two countries which they inhabit by turns, to enjoy all the condi- 
tions of heat, light, and moisture favorable to their well-being. There are 
birds of passage which travel several thousands of miles in a few days, 
and go from one continent to another over wide seas. Thus at the com- 
mencement of September, the stork, dreading the severe cold of North 
Germany, abandons the thatched roof to perch on a cupola of Egypt or 
Tunis ; then in the month of March, when the African climate becomes 
too dry and burning, it resumes its flight, and, crossing the Mediterra- 
nean, passes the high Alps, either on the e&st by the Engadine, or on the 
west by the Jura, and alights once more on its nest, respected by the 
peasant. 

In the climate of temperate Europe nearly a hundred birds, among 
them the crane, the lark, the j)assenger-pigeon, the quail, and the swallow, 
travel thus alternately from north to south, and from south to north, to 
avoid the extreme temperatures, and perhaps still more to find an abun- 
dance of food at all seasons of the year. It is even possible that certain 
species cross the equator during the migrations, and by this coming and 
going they constantly enjoy a summer temperature, now in one hemi- 
sphere, now in another. Several species of mammalia make similar jour- 
neys. The vast prairies of North America witness each year the immense 
migrations of the bisons, field-mice, and musk-rats defiling in innumerable 
multitudes. In mountainous countries, too, animals can easily change the 
climate without travei'sing vast spaces ; it is enough for them to climb the 
mountain, and then to descend again to the plain. Some of th^ monkeys 
of Hindoostan take refuge during the summer in the high valleys of the 
Himalaya as far as 10,000 feet high, and return to the low forests of Terai 
at the approach of winter ; in the same way the reindeer of Lapland fol- 
low the snow, which now accumulates, and now melts on the mountain 
slopes. 

26^ 



402 LIFE. 

To avoid the extremes of temperature, either the cold of winter or the 
too great heat of summer, certain species of animals have also the resource 
of bui'ying themselves in the ground. The greater part of the insects pass 
their existence as larvse under the bark of trees, under heaps of leaves, or 
beneath the superficial strata of the earth. Some species of moUusks and 
fish, several reptiles, and a few mammals, hide themselves also in the mud 
of the lakes and marshes, or in burrows hollowed out beforehand. Thus 
protected from the climate outdoors, the animals fall into a state of tor- 
por, during which their life remains partially suspended ; the temperature 
of their bodies sometimes sinks to freezing-point, and fish have even been 
seen completely frozen, without this apparent death having prevented 
their resuscitation later; respiration and circulation of the blood ai-e 
gradually slackened, and digestion ceases entirely; the organs, becom- 
ing temporarily useless, are restricted ; even the intestinal parasites are 
numbed with the animals upon which they live. This long period of 
sleep is, however, a phenomenon which is found much more generally in 
the vegetable woiid. For, in fact, all the plants of the frigid and polar 
zones repose in the winter, and only live by their stems and roots ; even 
in warm countries, the plants present a remarkable periodicity in their ex- 
istence.* 

Although the privilege of locomotion permits a number of animals to 
enlai'ge their domain considerably, the species do not the less remain sub- 
ject to climatal conditions, and all have an area of habitation limited ei- 
ther toward the pole by the severity of the cold, or toward the equator by 
too great heat. Each climate has its particular fauna, which, in order to 
live and propagate itself easily, requires certain normal conditions of tem- 
perature and moisture. There are animals which can not quit the torrid 
zone without perishing, or living an artificial life like most of those trans- 
poi'ted at a great expense to our zoological gardens ; other species die if 
they are taken from the northern countries, covered with ice during the 
greater part of the year. The field-mouse seen by M. Martins on the Faul- 
horn, and certain animalculge, such as the Desoria nivalis and the Podura 
hiemalis, have their dwelling in the snow, or on the ground covered by it. 
On the other hand, certain rotifers exclusively inhabit thermal waters ; a 
scarabseus, the Hydrohius orhicidaris, lives in the sources of Hammam- 
Meskoutine, the temperature of which is 131°. In the seas the whale 
and various cetacese are arrested by the warm waters of tropical lati- 
tudes as if by a barrier of flame, while the cachalot and the sea-cow swim 
only in the tepid waters of the equatorial ocean. f In the same way the 
coral insects are only seen in seas whose temperature is above 72° Fahren- 
heit ; at 60° they can still live, but without developing their branches. 
The Gulf Stream, which carries into the northern seas the warm water 
from the Antilles and Bahamas, carries also with it multitudes of south- 
ern species, which never stray either to the righ^ or left into the colder 
waters of the polar current. The two masses of water, flowing parallel 
* See above, p. 364. f Maury, Geographie de la Mer. 

m 



EFFECT OF LIGHT AND HEAT. 493 

to each other but hi an opposite dh-ection, have each their distinct fauna, 
whose barrier of separation is an imaginary line between twoteones of dif- 
ferent temperatui'e, varying according to the seasons and the advance of 
the waters. As to the superior animals which man brings with him into 
almost all the countries of the world, they are modified considerably un- 
der the influence of the climate. Horses and dogs brought from England 
to the Himalaya Mountains ai-e clothed with a thick wool that grciws 
among their hair ; in equatorial Africa, on the contrary, the dogs and 
sheep become bald, and fowls lose all their feathers, with the exception 
of the larger feathers of the win^.* 

The influence of light is shown also in a very remarkable manner by 
the atrophy, or even the complete supjjression of the organs of vision, in 
the fishes and other animals which inhabit the depths of caverns. f The 
color of the skin, too, changes in most animals, according to the brilliancy, 
of the rays that shine on them. The fauna of caverns assumes a dusky 
and uniform livery, which is lost in the surrounding darkness ; while out- 
side, in the splendor of the sunlight, the brightest butterflies and birds fly, 
like winged flowers, no less brilliant than those of the meadow. The an- 
imals of the tropics, especially the insects, fish, and reptiles, shine in much 
brighjter colors than those of similar species from the temperate and gla- 
cial zones ; thus, as M. Radau says, " The sun depicts itself in the fauna 
of a country." Finally, in ttfe same individual the action of light mani- 
fests itself by the contrast of colors, glittering on the back or upper sur- 
fa|;e of the wings, duskier on the belly or the under part of the plumage, 
which remains in the shadow. The habits of most species are also regu- 
lated by the alternations of light ; mammals, birds, reptiles, fish, insects, 
and mollusks have all their period of daily activity clearly defined, either 
by the setting or the rising of the sun. Among the insects especially, the 
awakening of each species by day, by night, or by twilight, is accom- 
plished with a singular regularity. The mosquitoes of certain tropical 
regions succeed each other in the air at a fixed hour well known by the 
natives, who, by imprisoning the insects which persecute them, are able 
to measure time no less easily than by that ingenious "floral clock" where 
each hour is marked J)y the expansion of a corolla. 

All the animals which inhabit the sea or the continents, equally require 
air in order to live ; but this air must be more or less pure, more or less 
charged with moisture, according to the species. Many birds, accustom- 
ed to rove through space, perish rapidly in the midst of a corrupted at- 
mosphere, and even their eggs can not be hatched there ; the intestinal 
worms, on the contrary, and the innumerable species of animals which 
feed on decaying matter, and thus perform the office of scavengers in na- 
ture, can accommodate themselves very well to an air mixed with impure 
gases. Fish, too, and other aquatic animals, with the exception of the 
cetaceoB and swimming birds, directly respire oxygen dissolved in water. 

^ * Schmarda, Geographische Verbreifung der Thiere, Jahrbuch von Behm. 

X See The Earth, the section entitled Springs. 



404 LIFE. 

As to moisture, it is equally indispensable to life ; but while certain spe- 
cies live 01^ the borders of marshes or rivers, in an atmosphere loaded 
with vapor, there are others, especially the numerous tribe of lizards, 
which delight in the rock or dry soil of desert lands destitute of water. 

The chemical composition of waters is most important for the organ- 
isms which live within it, and the fauna varies much in lakes, rivers, and 
seas, according to their proportion of salt and other substances ; it is thus 
that the Baltic, the saltness of which at its entrance is the same as that 
of the ocean, and which contains in its upper gulfs almost entirely fresh- 
water, pi-esents at its two ends two very distinct faunas, modified by 
gradual transitions toward the central part. As to the mineralogical na- 
ture of the soil, it has probably a somewhat slight influence on animal 
life, and the modifications which the fauna of the various soils exhibit 
ought principally to be attributed to the difiei-ence in the plants which 
serve as food to the animals. Thus some land mollusks are found exclu- 
sively on limestone formations, because the substances necessary for the 
formation of their shells are not found in the vegetation of other districts. 
The physical conditions of the soil are also of great importance to the 
species which hollow out burrows or subterranean passages. The mole 
can not trace its wonderful labyrinths in a sandy soil, which would fall in 
behind it ; and the ant-lion, which watches for its prey in a circular fosse 
at the foot of hillocks of shifting sand, woifld perish of hunger if it ven- 
tured upon clayey ground. It is a strange thing that even the color of 
certain species seems to correspond in a kind of secret harmony with the 
natural products around them. A humming-bird, that plunges with de- 
light into an open flower, glitters like the flower itself; many fish which 
live in rivers with a sandy bed seem to be only thin flakes of spangled 
sand ; moreover, a certain brown tnantis of Southern Africa lives only on 
a dark-colored ground ; another, entirely white, is only seen on the daz- 
zling chalk rocks ; the ptarmigan of Scotland is white as the snow in win- 
ter, and in the summer is dressed in plumage whose shades of pearly gray 
blends with the delicate tints of the lichens and heather. The green 
leaves of our forests have for inhabitants the tree-frogs and other little 
creatures which match the verdure ; while a butterfly, itself resembling a 
dead leaf, dances in the air among the dead leaves scattered by the wind ; 
an orthopterous insect even seems as if it were disguised under the form 
of a broken beech-twig, and we might think that it was one of these innu- 
merable fragments that the tempest has broken from the tree. On the 
River Amazon the air is filled at certain seasons with a species of white 
butterfly, flying in myriads, like snow-flakes in a storm ; but among these 
butterflys are some individuals of species ordinarily distinct in color, and 
which have disguised themselves in white in order to be lost in the im- 
mense crowd.* A How can we attempt to explain this remarkable phenom- 
enon, which c^stitutes the sole means of defense of the humming-bird, of 
the feeble i^ect, of the helpless parasite, excepting by the hypothesis of 
* Bates, Naturalist on the River Amazons. 



PROTECTIVE DISGUISES. 



405 



" natural selection " which Darwin has recently expounded so clearly. In 
the incessant struggle for existence dating from the very origin of the 
•species, all the individuals which can not defend themselves by strength, 
cunning, scent, or venom, inevitably perish ; those alqpe have the chance 
of escaping which, by their form and color, are not distinguishable from 
surrounding objects. It is these who, by the gradual disappearance of 
the individuals visible to animals of prey, pei'petuate the race, and, in 
the succession of generations, it is still the varieties most resembling the 
ground or plants on which they feed which save the species from destruc- 
tion. Thus, from generation to generation, anomalies never cease to ad- 
just themselves, and to assume in the end a jsermanent character. 



406 * LIFE. 



' CHAPTER X. 

FOOD OP ANIMAL SPECIES. — CONTRAST OP PAUNAS. — AREAS OP HABITA- 
TION. CHANGES IN THE SURPACE OP THE AREAS. BIRTH AND DISAP- 
PEARANCE OP SPECIES. 

Op all surrounding circumstances, that which most influences species, 
as we can easily understand, is their food. In the sea, where the flora is 
relatively poor, and where the fauna, on the contrary, is developed with 
such an astonishing abundance, animals and animalcules are almost all 
carnivorous; the herbivorous kind are few in number. On the dry land, 
on the contrary, the vegetation predominates so largely that most of the 
animals live upon plants, either their shoots, leaves, flowers, fruit, stem, 
bark, or roots. The largest animals, the elephant, rhinoceros, eland, and 
girafie, as formerly the mammoth and the mastodon, feed on plants, 
grasses, and leaves. Most birds live on seeds, and with many of their 
species it is to the need of finding food, and not to the alternations of cold 
and heat, that we should attribute their annual or daily migrations. The 
life of the greater part of animals is only one long journey. Urged now 
by hunger, now by the necessity of seeking their safety, they come and 
go'incessantly from one region to another — from the forests to the mead- 
ows, from the mountains to the plains, from solitudes to cultivated lands. 
In the valley of the Lower Mississij^pi there is a kind of swallow, known 
under the name of martinet, which every morning flies in immense flocks 
toward the pine forests of the left bank of the river, and every evening 
returns and alights like a cloud on the marshy groves of cypresses on 
the right bank. 

It is principally among insects that the intimate connection uniting the 
animal to l^he vegetable world shows itself Many plants have their spe- 
cial fauna of insects ; and of this eager multitude which devours them, 
some attack only the leaves, others the wood, qx various other parts. The 
nettle has no less than forty species which are born, live, and die on its 
stem. The birch, the willow, and the poplar are each also the exclusive 
home of numerous ti'ibes of insects ; the oak alone nourishes at least one 
hundred and eighty-four species — more than the continent of Europe con- 
tains in mammals ; every other tree than that of which they eat the wood 
or the bark is an unknown world to them. Thus no insect of Cayenne 
has become a parasite of the cabbage, carrot, vine, or cofiee-plant, because 
these plants have been imported from distant countries, and no corre- 
sponding species is to be found in the country.* 

The area of habitation of each animal, large or small, which lives upon 
one or several vegetables, being necessarily limited by the area of the 
* Schmarda, Geographisches Jahrhuch von BeJim, 1866. 



HARMONY OF FLORAS AND FAUNAS. . 407 

plants themselves, it necessarily results that the carnivorge are also quar- 
tered in the vegetable region which is inhabited by the prey that feeds 
theip. Beyond the tropical zone in countries where winter periodically 
suspends the life of the forests and meadows, the parasites of trees and 
grass are also, for the most part, condemned to sleep, either in the earth 
or in the plant they feed upon, and the beasts of prey which have not a 
period of winter sleep must suffer hunger or change their country, till the 
return of spring. Finally, the destruction of a plant always has, as a di- 
rect consequence, the disappearance of the special fauna which was at- 
tached to it. If man fells a forest, uproots bushes, or drains a marsh, at 
the same time a world of animals is destroyed or exiled. 

The richness of the fauna is thus in intimate connection with that of 
the flora : where vegetation springs from the soil with most vigor and 
abundance, there also animals live in the greatest multitudes. Neverthe- 
less, we must not think that the animals of the largest size inhabit pre- 
cisel)'^ those countries where the most gigantic trees grow. In this re- 
spect there is rather a contrast ; the great pachyderms of Africa feed on 
plateaux destitute of trees in many places, and covered with thin grass ; 
the enormous white bear of the northern regions inhabits snow and ice- 
fields, far from all forest vegetation. On the other hand, the splendid 
forests of Brazil give shelter to relatively small species. The largest is 
the tapir, much inferior in dimensions to the huge animals of Africa, The 
most remarkable fact in the distribution of the largest species of animals 
is, that they inhabit the most extensive countries ; it is in the Old World 
that the largest members of the animal world live ; and the long-tailed 
monkeys, tapirs, vicunas, jaguars, and pumas of America are much less in 
size and strength than the gorillas, elephants, camels, tigers, and lions of 
Africa and Asia. 

The number of species of animals is likewise connected with the extent 
of the countries. There does not exist one example of an island whose 
fauna is richer than the neighboriYig continent ; in almost all we find an 
enormous inferiority in this respect. Great Britain, a fragment detached 
from Europe, has fewer animal forms than Germany or France ; Ireland 
has less than England ; Sicily less than Italy. When the Europeans first 
landed on the Antilles, nearly four centuries ago, the sole indigenous 
mammals, with the exception of bats, which could fly over the straits, 
were four or five species of rodents, oae of which exists still. Yet the 
very varied vegetation of the mountains, valleys, plains, marshes, and 
shores of Cuba, Hayti, and Jamaicaj would have sufliced for the support 
of a multitude of species. In the same way, before the arrival of the En- 
glish navigators, New Zealand had no other mammals than two species 
of bat, a rat introduced, perhaps, in a ship, a sort of otter, and a leaping 
animal, only the remains of which were seen.* A real harmony is natu- 
rally established between each region and its particular fauna so com- 
pletely, that the geologist, discovering very varied fossils and large skele- 
* F. vou Hochstetter, New-Seeland. 



408 LIFM 

tons in an island of small dimensions, is able to affirm that it once formed 
part of a vast continent. 

In order to resolve the important question of the distribution of ani- 
mals, the naturalist must go back to the anterior ages of the earth, dur- 
ing which the continents were otherwise disposed than they now are. 
Thus the monkeys on the Rock of Gibraltar bear witness to the ancient 
continuity of the coasts between Spain and Barbary. In other places, in 
consequence of the change in the forms of the continents, the former spe- 
cies contrast strangely with the present ones ; only a strait separates two 
fauna, born at an interval of thousands and perhaps millions of centuries. 
This is the contrast observed between the archipelago of Sunda and the 
group of the Australian islands. Between Bali and Lombok, which seem, 
however, to form part of one land cut in two by the waves, and which a 
strait fifteen miles long scarcely separates, the contrast of the faunas is 
as complete as between Europe and America. On one side quite modern 
species live, as if the ancient types had been gradually renewed by the 
neighborhood of the vast continent of Asia ; on the other, the animals 
have been preserved without a change in their physiognomy. In Aus- 
tralia we find neither cat, wolf, bear, nor hyena ; neither stag, sheep, ox, 
elephant, horse, squirrel, rabbit, nor any of those species of quadrupeds 
which we meet with in all other parts of the earth ; but instead, how 
many animals of ancient forms which to us seem most strange ! The 
whole Australian fauna resembles that which formerly occupied the seas 
and shores of Europe during the Jurassic period ; it is necessary to trace 
the course of the ages back to that epoch, to find animals which recall 
those of New Holland.* 

Whatever may be the enormous part to be referred to the earlier con- 
ditions of the globe to explain the present distribution of the animal sjje- 
cies, it is certain that there is now a remarkable harmony between the 
configuration of the continents and seas, and the crowd of living creatures 
which inhabit them. Every terrestrial' or maritime space, clearly limited 
by some great geographical feature, such as a strait, isthmus, mountain 
chain, or plateau, every district distinct from the countries bordering upon 
it by the nature of the .soil, and especially by the climate, possesses also 
its peculiar fauna, having but a relatively small number of representative^ 
in common with those of other regions. The French plains which stretch 
to the north of the Pyrenees, and the Spanish valleys of the tributaries 
of the Ebro, contrast with each other in a sufficiently striking manner, 
both by certain species of animals, and by their vegetation and the gen- 
eral aspect of all nature. Similarly, the difference is very gi-eat for the 
living organisms as well as for the soil on the two slopes of the Aljjs ; in 
France, in the stony and desolate basins of the Drac, the Durance, and the 
Verdon ; in Italy, on the fertile banks of the Stura, the Po, and the Doire. 
A narrow isthmus separating two seas, separates at the same time two 
worlds of different species. It is thus that, of one hundred and twenty 
* Wallace ; see The Earth, the section entitled The Earliest Ages. 



AREAS OF HABITATION. • 4O9 

zoophytes, the Mediterranean has only two in common with the Red Sea, 
and yet the slight sandy barrier of Suez is of relatively recent formation 
in the immense series of geological ages. The slender isthmus of Central 
America, which lies between the Pacific and Atlantic oceans, is an insur- 
mountable baiTier to the two faunas, and the waters separated by a dis- 
tance of a few miles only are inhabited by totally different species; there 
scarcely exists, Darwin tells us, a single fish, mollusk, or cetacean, which 
is common to the two oceans. Even the course of the River Amazon 
serves as a limit to multitudes of species ; there are birds which never 
venture to cross it, and whose area of habitation is strictly limited either 
to the right or left bank. 

In consequence of the great diversity of the present conditions of cli- 
mate, soil, and food ; in consequence, too, of the infinite multitude of causes 
which, in the earlier ages, may have favored or hindered the development 
of the species engaged in the struggle for existence, the areas occupied 
by different animals are most unequal in extent. There are cetaceoe, swim- 
ming birds, and echinoderms, which live in all the seas, and gnats, which 
fly in clouds over the marshes of all the continents ; on the other hand, 
certain species are only found in a very limited region. Some reptiles 
are peculiar to a single district of the Rocky Mountains or the plateau of 
Utah ; a certain humming-bird has been discovered in only one valley of 
the Andes ; every lofty volcano of Eucador, as Pichincha, Chimborazo, 
and Carahuirazo, is a separate world, having its own special fauna.* In 
the immense River Amazon three species of a fish called arias are found 
only to the west of the Island Marajo, in a space of scarcely two leagues, 
at the place where the mingling of the mud raised by the conflict of the 
sea and river takes place.f 

Besides, the different areas of habitation change incessantly during the 
course of ages, according to the modifications of soil and climate. Man, 
too, who is also a geological agent, and one of the most active, has taken 
an enormous part, either directly or indirectly, in the distribution of ani- 
mals ;I but apart from this decided influence due to human intervention, 
it is certain that all the variations of the surrounding circumstances pro- 
duce corresponding variations in the distribution of species. If cold or 
heat increase in a country, the winds become stronger or weaker, the rains 
increase or diminish ; or if the soil be renewed by alluvium, or saturated 
w^th salt by an irruption of the sea, or if a marsh be formed or dried up, 
a number of species of animals will advance or retreat to find conditions 
of existence which are more favorable to them, and also to seek food which 
suits them. Thus various birds of the Upper Engadine have established 
themselves in the lower valleys, and the magpie has even entirely quitted 
the district.§ This is a phenomenon which all naturalists have observed : 
they have even ascertained many apparently inexplicable examples of 
migrations, so imperceptible to man have been the modifications of cil-- 

* Moritz Wagner. + Da Silva Continho. 

X See below, the section entitled The Work of Man. § Michelet, la Montague. 



410 • LIFE. 

cumstances which have produced these changes in the areas. Thus the 
whales ceased to visit the Faroe Islands for twenty-two years — from 1754 
to 1776; in Sweden a number of species have completely disappeared 
from the country, and have then returned, like exiles re-entering their na- 
tive land, to inhabit again the country of their ancestors.* Nor is this 
all: not only may animals enlarge or restrict their areas of habitation, but 
they may even completely disappear ; and zoological history, hardly com- 
menced a few centuries ago, already has to relate the extinction of sev- 
eral species. On the other hand, new creatures take the place of those 
that have departed, and during the succession of ages the fauna is re- 
newed by the formation of varieties which become more and more con- 
stant, and at length present all the characters of species. How otherwise 
can we explain the remarkable fauna described by Darwin, which belongs 
especially to the Galapagos Islands, and is neither found in the archipela- 
goes of the South Sea nor on the neai'est continents ? 

* Schmarda, Geographisches Jahrbuch von Behm, 1866. 



• GREAT TERRESTRIAL FAUNAS. 411 



CHAPTER XL 

GREAT TERKESTRIAL FAUNAS. — HOMOIOZOIC ZONES. 

Every district distinguished from those that surround it by a certain 
number of animal forms has thereby a special fauna ; but naturalists usu- 
ally take this word fauna in a more general sense, and apply it to a col- 
lection of species inhabiting a vast geographical region, beyond which 
the majority of forms are completely changed. For the rest, as might be 
expected, savants are fai* from agreeing on the limits of these regions, for 
these frontiers have no real existence, and in the multitude of living 
creatures, whose areas of habitation mingle with and intersect each 
other, there are several which belong at the same time to many districts. 
Schmarda, one of the most eminent classifying zoologists, enumerates 
twenty-one great terrestrial faunas, including those of Madagascar, the 
Sunda Islands, and Oceania. These various zoological provinces, each 
one of which possesses only a small number of species in common with 
the neighboring provinces, have still many points of resemblance with 
each other, owing to the multitude of animals which approach each other 
in form and structure, and fulfill analogous functions in nature : these 
species, which in the fauna of a continent take the place occupied in a dif- 
ferent country by other animal forms, are termed, scientifically, represent- 
atives. Thus the camels of the Old World are replaced in America by 
llamas and vicugnas ; the horses of Asia have the zebras as relations in 
South Africa ; the ostriches of the Sahara are represented in Australia by 
emus, and in the Argentine pampas by rheas. In this respect the animal 
world presents the same harmonies as the vegetable world. 

The greatest analogy between the two organic series is found also in 
their order of distribution over the circumference of the globe. All the 
circumpolar regions of the northern hemisphere in America, in Europe, 
and in Asia are inhabited by identical species, or at least present a great 
appearance of relationship to each other; the same flora and the same 
fauna occupy the extremities of the continents ; but toward the south, in 
proportion as the lines of latitude enlai'ge their circles, and the Old and 
New World withdraw from each other, the living creatures that people 
them, animals and plants, difier more and more. The number of organ- 
isms common to the lands separated 1by the Atlantic and the Pacific 
Oceans gradually diminishes, and in the tropical regions the contrast be- 
tween them is complete. At the same time, animal and vegetable spe- 
cies become more and more numerous in the direction from the pole to 
the equator. In Spitzbergen, M. Charles Martins found only four terres- 
trial mammals ; twenty-two species of birds, all of them being n\igratory 
with one single exception, flying beyond the mountains of this archipel- 



412 LIFE. 

ago ; ten sorts of fish inhabit its coa?ts, while the lower orders of animals 
are rej)resented by only a very small number of forms : only twenty-three 
insects and fifteen mollusks have been discovered there. To the south 
of the northern regions the number of species, genera, and families is 
multijDlied ten-fold, or even a hundred-fold ; and in the equatorial coun- 
tries, where vegetation exhibits all its luxuriance and wealth, the fauna 
shows also a marvelous variety of organisms, and its types are of the 
most beautiful and dazzling colors. A single naturalist, Bates, after a 
stay of eleven years on the banks of the Amazon, brought back a zoolog- 
ical collection of 14,712 animals, 8000 of which were new to science. 
How many must still remain to be discovered, especially among the in- 
sects and Annulosae. According to Agassiz, the Amazon alone possesses 
three times as many different fish as the immense basin of the Atlantic. 

It is true that, if the countries nearest the pole are poor in species, 
these species themselves are, for the most part, represented in immense 
numbers. On all the promontories and in all the fjords of the Hebrides, 
the Shetland and Faroe Islands, Norway, Spitzbergen, and Nova Zembla, 
the shelves of rock, similar to the shelves of an amphitheatre, are occu- 
pied, far as eye can see, by ranks of birds ci-owded together like an army 
of soldiers. When these prodigious flocks of birds set off in search of 
prey, they rise like clouds, and man has only to shoot at hazard in order 
to strike down his victims, unless, armed with a stick, he prefers to dis- 
patch the females, which, screaming with rage, remain devotedly cover- 
ing their broods. 

The oceanic faunas must necessarily present a greater regularity in 
their distribution than the terrestrial faunas, for they are not liable to 
such changes in physical conditions as affect the surface of the land. 
The sea is not, like the land, full of obstacles which check the distribution 
of animals, and modify in various ways the configuration of their domain. 
Thus the limits of each great maritime fauna are precisely those of the 
basin where this fauna is developed ; to the east and west, they are the 
shores of the continents ; to the north and south, they are the different 
climates which arrest the species, and cause them to be succeeded by 
other animal forms. 

Edward "Forbes was the first who attempted to draw a map of the dis- 
tribution of living organisms in the seas, and since then the general re- 
sults which he indicated have been confirmed in great part by the vari- 
ous savants who have followed him in this way. Each region or mari- 
time province is characterized by species which may serve as representa- 
tives of all the other organisms of the province, and which attain their 
greatest development in these parts. From all sides of the central zone, 
where the fauna peculiar to the province shows itself in all its richness, 
the species go on diminishing by degrees toward the other regions, and 
are finally replaced by the prevailing species which in this portion of the 
sea constitute the bulk of the marine population. Forbes compares the 
domain of each of these fauna to a nebula, the luminous points of which, 



EXTENT OF M AMINE riiOVINCES. 413 

united in the centre in a brilliant mass, become less and less numerous as 
they diverge from the centre, and on the circumference constitute noth- 
ing more than scattered traces. The oceanic fauna, consisting as they 
do of a series of zoological nebulae, do not, however, differ in this resj^ect 
from the continental fauna; but, owing to the facilities for migration af- 
forded by the sea to free-swimming animals, the maritime provinces in 
which any particular species predominates are wider in extent than in 
an analogous district of terra firma. Generally speaking, places sitiiated 
in the same latitudes are frequented by the same sj^ecies ; a remarkable 
instance of this fact may be observed in the Mediterranean, where, from 
Gibraltar to Alexandria, there is scarcely any difference in the marine 
fauna. With regard to the limits of these regions common to the same 
groups, their extent can very seldom be clearly defined, except where 
ocean currents of different temperatures come into contact. The change 
from one province to another generally takes place without any sudden 
transition, for the action of currents, tides, etc., endeavors incessantly to 
establish an equilibrium in the temperature of the ocean, and prevents 
any well-defined boundaries of the limits of any forms of life. 

It is, nevertheless, necessary to take into consideration every condition 
which tends to modify the general outlines of each geological province, 
the form of its sea-coast, the nature of its bed, the rapidity of its currents, 
the height of its tides, and the saltness of its water.* 

These various provinces are the extensive regions which Forbes has 
designated by the name of homoiozoic zones (zones embracing a similar 
kind of life). They encircle the earth like the climatic zones to which 
they correspond, and, sjjeaking generally, their limits are formed by the 
isothermal lines; they also change their position in harmony with these 
ideal limits, sometimes rising toward the north, and at others curving 
toward the south. 

The great median zone is that of the equator and the tropics, the most 
important part of which comprises the whole of the Indian Ocean and 
the central belt of the Pacific, from the coasts of Australia, Borneo, and 
Japan, to those of Mexico and Colombia. In this region, for the most 
part, marine animals present the most brilliant colors and varied forms. 
This, too, is the region where the waters swarm with the greatest number 
of organisms, and corals and madrepores construct their circular islands, 
which stud the coasts of Asia as far as the middle of the Southern Ocean. 
Between equatorial Africa and America this homoiozoic zone is still con- 
tinued, in spite of the interposition of two continents; on the coasts of 
Florida, the Bermudas, the Antilles, the Guianas, and Brazil, mollusks, 
echiuoderms, and corals, similar to those of other equatorial seas, multi- 
ply abundantly ; the species are different, but the general types are the 
same. 

To the north of this median zone, which extends round the globe M'ith 
an average breadth of 3700 miles, there is another encircling zone, Avhich 
* Natural History of the European Seas. 



414 ' LIFK 

is much narrower, and rendered very irregular by the variations of cli- 
mate which toward the north are produced by winds, maritime currents, 
and the different conditions of the opposite continental coasts. This 
northern "circumcentral" zone takes its rise in the Atlantic, on the coasts 
of Georgia and the Carolinas ; then, spreading out toward the east, it 
washes the coasts of Morocco and of the Iberian peninsula. Beyond the 
Straits of Gibraltar it embraces the Mediterranean, where there ai-e fish- 
eries for the tunny, sjDonge, and coral. In this sea the species show a 
gradual diminution from west to east, and in the inclosed basins in the 
interior of the continent, the Black Sea, the Caspian, and the Sea of Aral, 
they are even much less numerous. In the Pacific, this same zone, the 
limits of which are however scarcely known, stretches from the coasts of 
the Corea and Japan toward those of California. 

The third zone, which is situated about the middle of the temperate 
latitudes, has received the name (not, however, a very appropriate one) 
of the neutral northern zone. Like the last-mentioned zone, it curves 
round and spreads out across the Atlantic from the coasts of America to 
those of Europe. It is narrow along the shores of Virginia and Dela- 
ware, but it widens out toward the north-east with the Gulf Stream, and 
embraces all the Celtic seas of the peninsula of Brittany, Ireland, Scot- 
land, and the Shetland Isles. The Baltic Sea and its gulfs are mere de- 
pendents on this zone. The great herring fisheries are carried on in this 
homoiozoic zone. 

The most northerly zone which is characterized by fisheries for cod and 
other fish of a similar nature, likewise follows the immense curve of the 
Gulf Stream, and stretches from east to west. Beginning at Cape Cod, 
in the Bay of Fundy, it embraces Iceland and the adjacent seas, and wash- 
es the coasts of Norway and Lapland up to North Cape. In the Pacific, 
this zone, known as the northern circumpolar zone, assumes, like the neu- 
tral zone, a circular tendency, owing to the great current of Japan and 
the south-west winds, which in this part of the ocean bring about a cir- 
cuitous movement similar to that of the Gulf Stream. 

Lastly, the Arctic Seas are occupied by the polar homoiozoic zone, the 
extent of which comprises the whole of the spherical cap from the pole to 
Labrador, the Gulf of Obi, Behring Straits, and Kamtschatka. In this re- 
gion, the inhabitants of the sea, generally speaking, are of rather dull col- 
ors, and the species are much less numerous than in the southern zones ; 
but, on the other hand, these species are for the most part represented by 
a great number of individuals. 

In the southern hemisphere, the homoiozoic zones follow one another in 
the same order as in the opposite hemisphere, and exhibit similar transi- 
tions between the respective typical species ; but, it must be confessed, 
the comparative extent of these various zones is very impei'fectly ascer- 
tained. All we positively know is, that to the west of South America the 
domain-of each of the marine faunas curves round toward the north, car- 
ried away, so to speak, by " Humboldt's Current," which runs along the 



HOMOIOZOIC ZONES. 41 5 

coast. For the present, the lines of temperature are the oniy data we 
have for fixing, somewhat inaccurately, the limits of zones. It will be the 
task of future explorers to determine them more exactly. It would be 
equally difficult to state at the present time in what proportion species 
of marine animals diminish from the equator to the poles. In order to 
solve this question approximately, it would, in the first place, be neces- 
sary to ascertain the quantity of organic beings contained in the various 
oceans. All we positively know is, that in the European seas the species 
offish show a diminution of nearly two-thirds in the northern as compared 
with the southern seas, since in the Mediterranean 444 are met with, while 
in the Scandinavian seas there are found scarcely 170. Mollusks resist 
better the influences of climate, for about 300 have been reckoned on the 
coasts of Sweden and Norway — that is to say, nearly half as many as on 
the shores of the Mediterranean.* During the only voyage of discovery 
conducted by Captain Wilkes, the American naturalists succeeded in col- 
lecting in the tropical waters of the South Sea 829 species of fish, 900 
crustaceans, 2000 mollusks, 450 corals, and 300 zoophytes. 
* Forbes, Natural History of the European Seas. 



416 ■ LIFE. 



CHAPTER XII. 

DISTEIBUTION OF SPECIES ON THE SLOPES OP MOUNTAINS AND IN THE 
DEPTHS OP THE SEA, 

The gradation of climate on the slopes and heights of mountains, simi- 
larly to their succession in the direction of the poles, brings about, as its 
necessary consequence, a rapid diminution of animals from the fertile 
plains at the base to the snowy summits of the mountains. If the nat- 
uralist scales some solitary lofty peak in the torrid zone, he will see the 
number of animal species rapidly diminishing, exactly as if he were trav- 
eling toward the temperate regions, and then toward those of the pole. 
At last, when he reaches the lower limit of perpetual snow, where vege- 
tation almost entirely disappears, there remain but very few representa- 
tives of the animal world ; and those which still exist in these upj)er re- 
gions are mostly minute beings, like the animalculae of the snow, and 
small quadrupeds which bury themselves in the snow, similar to the vole, 
which is met with on the summits of the Alps.* Not only do the species 
graduallv diminish on the slope of the mountain — a fact, however, which 
is easily accounted for by the deficiency of food, the increase of cold, and 
the rarefaction of the air ; but also the animals met with in the upper re- 
gions are not the same as those of the lower slopes, and in their form, 
coat, and habits resemble the animals of the polar zone. The faunas of 
the Andes and the Alps bear more yesemblan-ce to those of Spitzbergen 
than to those found in the plains at their feet, which are situated at a dis- 
tance of a few thousanjl feet.f Nevertheless, storms, gusts of wind, and 
water-spouts frequently blend the locally arranged faunas one with anoth- 
er ; and, as we traverse the snow on the summits, we rarely fail to see the 
great white surface dotted over with the remains of insects which have 
been carried up from the valleys by atmospheric currents. Sometimes 
even a few stray butterflies fly by chance into these gloomy solitudes, 
where the cold during the night is certain death to them, unless some 
favorable wind carries them back to the warmth of their native meadows. 
As far as birds are concerned, numbers of them fly freely up to the lofti- 
est summits. M. Jules Remy has seen myriads of humming-birds flying 
noisily round the crater of Pichincha, and the traveler, scaling the proud- 
est heights of the Andes, sees far above his head the great condor soaring 
majestically in the blue sky. 

On dry land, most animals mhabit districts but slightly elevated above 
the level of the ocean; following the same rule, a large majority of the in- 
habitants of the seas — infusoria, annelids, crustaceans, fish, and other crea- 
tures — exist in the liquid strata of the surface, and in the neighborhood of 
* Charles Martins, du Spitzberg au Sahara, p. 340. t See above, p. 379. 



niSTIUBUTION IN DEVTH. 41 7 

coasts. This must be tlie case ; for it is only along the sea-shores that we 
liiid rocks which are covered with shells, caves, and crevices, where the fish 
take refuge, and also the forests of sea-weed, which are used both for shel- 
ter and fo«d by multitudes of organic beings ; there, too, the rivers con- 
vey all the animal and vegetable debris from the main-land, which serves 
as food for the inhabitants of the sea. Farther out to sea, every stray 
piece of sea-weed, and every floating mass of the same, is also a muster- 
ing-point round which a perfect little world lives and moves ; even far 
from the shore and shallow water, life, although less stirring in compari- 
son with that of the coast, is nevertheless wonderfully active in the upper 
strata of the sea; for there the waves take their rise on the surface, and 
their movements are as necessary to the organic beings of the sea as the 
breath of the wind is to the life of terrestrial animals ; these upper strata 
are also the portions of the ocean into which the light penetrates. Ac- 
cording to the experiments of Wilkes, the rays of light would not descend 
beyond eighty-two fathoms ; and this point, therefore, would mark the 
limits determined by the darkness habitable by marine animals and vege- 
tables. Therefore the zone of contact where the sea meets the atmos- 
phere, and especially in the vicinity of continents, is Avhere "aquatic life 
swarms in the greatest abundance. On land, the conjunction of several 
geological strata fertilizes the soil, and consequently promotes a greater 
degree of activity in the development of the difierent germs; in the same 
way, the contact of the three elements, water, wind, and shore, draws or- 
ganic beings into the surface strata of the ocean, and thus enfolds the 
globe, as it were, in a living envelope. 

The shallow parts of the sea, especially in the vicmity of the coasts of 
Europe and the United States, have been already explored with the great- 
est possible care by Edward Forbes, in order to point out the approxi- 
mate depth of the superincumbent layers of flora and fauna. Each of 
these zones is distinguished by organisms, or groups of organisms, pecul- 
iar to it. They do not, however, with the exception of the upper strata, 
present any clearly-aefined boundary ; there are, moreover, a great num- 
ber of genera and sub-genera, which are common either to all the eleva- 
tions, or to two or three of them. 

The first zone, or that of the shore, is limited by the extreme lines of 
ebb and flow, and, according to the height of -the tide, is from half a fath- 
om to eleven fathoms in depth; in this stratum a multitude of organisms 
live and move, because it is in turn occupied both by the water and the 
air. The second stratum, called the laminarian zone, from a species of 
sea-weed which there throws out its long band-like leaves, resembling 
leathern straps, has a depth of about sixteen fathoms below low-water 
mark. This is the principal habitat of marine plants, fish, mollusks, and 
crustaceans. Most of the species found here are remarkable for the brill- 
iancy or even splendor of their color^, which they owe to the luminous 
rays refracted from the surface of the water. The third, or coralline stra- 
tum, extends as far as thirty-two fathoms below the last-mentioned stra- 

27 



418 * ,LIFE. 

turn ; vertebrate or invertebrate animals are here represented by numer- 
ous species, but vegetation begins to be scarce. The fourth stratum of 
the European seas, which, according to Edward Forbes, has not a depth 
of more than 110 to 330 fathoms, and beneath which extend th« vast soli- 
tudes of the uninhabited seas, is without doubt less thickly jjopulated than 
the body of water above it, into which the light of the sun succeeds in 
making its way, and the mollusks, crustaceans, and annelids which are 
found there are for the most part of a sombre hue ; but even at this point 
we have not reached the limit of life. 

It is an indisputable fact that marine animals exist at a much greater 
depth than naturalists, until very recently, allowed. Although soundings 
taken at great depths in the open sea have not at present been very nu- 
merous, and though in most cases the sounding-line did not bring up any 
traces of sand or mud from the bed, most savants, relying solely upon 
this negative evidence, predicted that the lowest depths of the ocean were 
abiotic spaces — that is to say, absolutely destitute of living organisms. 
Even when several mariners had obtained proofs to the contrary, many 
well-known savants, such^as Edward Forbes, Godwin-Austen, Agassiz, de 
la Beche, were still of opinion that below a certain depth, fixed by some 
at 165 fathoms, and by others at 330 fathoms, all animal or vegetable life 
was impossible. Each depth of five and a half to six fathoms involving 
a pressure of water equal to that of an entire atmospheric column, it was 
thought that the general proximate conditions would be so changed at 
the bottom of the ocean, that the development of any organisms in these 
vast depths would be rendered absolutely impossible. It was also a fore- 
gone conclusion that living beings could not live under a pressure of hun- 
dreds or perhaps thousands of atmospheres. According to an hypothesis 
which is just as much in opposition to the facts, neither plants nor insects 
can exist on the highest mountains ; in the same way, by a kind of polar- 
ity, the bed of the ocean was supposed to be nothing but a vast solitude. 
The hardiest among marine animals would then be the fine coral of the 
coasts of Norway, the Lophelia prolifera., the rose-colored branches of 
which are found attached to rocks at a depth of 330 fathoms from the 
surface. 

Nevertheless, since the year 1818, the results of many soundings have 
contradicted the opinion laid down by most naturalists. In Baffin's Bay, 
John Ross brought up from the bed of the sea some small crustaceans, 
annelids, and echinoderms, and in the regions inhabited by these animals 
the depth determined by the sounding-line varied from 110 to 1033 fath- 
om§. On the other side of the globe, in the Antarctic seas, James Ross 
discovered, in 1814, some living crustaceans at a depth of 393 fathoms; 
but this fresh evidence, verifying the existence of organisms in the lowest 
depths of the ocean, was ignored like the former. Some time after, the 
soundings made between Ireland ,and Newfoundland along the " tele- 
graphic plateau'''' brought to the surface a large number of small organ- 
isms, foraminifera, polycistina, and diatomacea. Further, the sounding- 



THE INHABITANTS OF THE mEEP. 419 

line brought to light 116 different species of these aniinalcuUt?, taken from 
a depth of 3660 fathoms between the Philippine and Ladrone islands. 

Lastly, in the voyage of exploration undertaken by M'Clintock, in 
1860, across the North Atlantic, Dr. Wallich definitely solved the ques- 
tion by indisputable proofs. At the south-east of Iceland the dredge de- 
tached a fragment of a serpula, the flesh of which was still fresh, and 
some small living shell-fish, from a rock at a depth of 6*71 fathoms. In 
addition even to this, another sounding, made at a depth of 1240 fathoms 
— that is, at a point where the weight of the body of water exceeded 200 
atmospheres — brought up several small shell-fish and thirteen starfish, 
one of which was not less than four and a half inches in breadth : these 
animals reached the. surface of the water alive, and for a quarter of an 
hour they incessantly worked about their long spike-covered arms ;* be- 
sides, the remains of the foraminiferte which were found in the digestive 
organs of the echinoderms allow no doubt as to the fact that these infe- 
rior organisms likewise exist at a depth of more than 1200 fathoms in the 
ocean. Since Dr. Wallich's discovery, Torrell brought up from a depth 
of 1430 fathoms, in the sea of Spitzbergen, a crustacean of brilliant colors. 
The same fact applies to the Mediterranean; for when the telegraphic 
cable which joins the island of Sardinia to the coast of Genoa was broken, 
its fragments were found to be covered with polyps and shell-fish, bring- 
ing the wire in some places to the size of a hogshead. Subsequently, the 
submarine telegraph between Sardinia and Algeria was also broken, and 
Mr. A. Milne Edwards recognized on a fragment of the cable, fished up 
from a depth of 1000 to 1500 fathoms, a large number of animals, which 
must all have existed in the bed of the sea on this wire laid down by hu- 
man agency ; for their forms were molded round the iron on which they 
rested, and their soft parts were still in a state of preservation. Among 
these creatures there were found serpulae, a species of oyster, a highly-col- 
ored pecten shell, and, lastly, some polyps which hitherto had not been 
met with in any part of the Mediten-anean, and w^ere thought to exist 
only in a fossil state. f This is not all: Ehrenberg has shown that lumi- 
nous animalculae exist at the bottom of the Gulf of Mexico ; and this un- 
expected fact admits of the supposition that the depths of other seas and of 
the vast ocean are not lost in unfathomable darkness. It may therefore 
be concluded that at a depth of even thousands of fathoms light is not 
altogether wanting, and that it shows itself periodically, or even constant- 
ly — thus explaining why the eyes of species taken from deep waters are 
not atrophied like those offish and insects found in dark caverns. J 

Thus the depths of the ocean are not a vast desert where the movement 
of hidden counter-currents is the only evidence of terrestrial life; even in 
the midst of these regions, where a ray of light never penetrates, there are 
beings which are born there, which live there, and which there find their 

* Wallich, Atlantic Sea-bed, p. 69. 

t Annales des Sciences Naturelles, 4th series, 1861. 

X Mittheilungen von Petermann, vol. vi., 1867. 



420 • LIFE. 

graves. Doubtless most of those beings, like the inhabitants of caverns 
on terra firma, are dressed in a sombre hue ; but this is not a zoological 
law, for those very species which have been discovered at the greatest 
depths — namely, the echinoderms, found by Wallich in the sea of Iceland, 
and the crustaceans taken by Torrell from the bed of the Frozen Sea — pre- 
sent tolerably bright colors. By gradually adapting themselves, either 
by migration or by the effect of a slight depression of the bed, to their 
location in these deep waters, these creatures have preserved the specific 
brilliancy of their color which their ancestors doubtless owed to the vivid 
light with which the superficial strata of the ocean are imbued.* As far 
as marine plants are concerned, sea-weeds properly so called have not yet 
been noticed growing at a depth of more than two hundred and eighteen 
fathoms : the only organisms which could be called vegetable which have 
been found in the depths of the ocean belong to the primitive order of 
diatomaceae. 

*5j.* Still more recent dredging researches, carried on by Carpenter, 
Wyville Thomson, and Jeffreys in England, Count Pourtales in the Uni- 
ted States, and Sars in Sweden, in depths varying from 200 to 650, and 
even up to 1400 fathoms, fully justify the inference that there exists a 
varied and abundant submarine fauna at depths which had generally been 
supposed to be azoic. They also completely disprove the earlier doctrine 
that an increased amount of bathy metric pressure must be prejudicial, if 
not fatal, to higher forms of animal life. 

The presence of bright colors in shells and crustaceans obtained from 
these vast depths, almost certainly proves that light — though greatly mod- 
ified — does penetrate even to the inmost recesses of the deep sea. — PI. W. 
* Wallich, North Atlantic Sea-bed, p. 135. 



GEOLOGICAL LABORS OF ANIMALS. 421 



CHAPTER XIII. 

GEOLOGICAL LABORS OF CERTAIN ANIMAL SPECIES. — CORAL REEFS AND 

ISLANDS. 

There are very few animals which, in order to obtain their prey or 
to construct their habitations, disturb the ground so forcibly as to leave, 
either on the surface or in the upper strata of the earth, traces of their 
work. Rabbits, foxes, " prairie-dogs," and marmots dig out burrows ; 
moles and musk-rats make their way under-ground, like miners, through 
long avenues or labyrinthine galleries ; white ants construct " high obe- 
lisks of clay ;" but when the animal builders have left their hidden vaults 
or visible palaces, they do not long resist the rains, vegetation, and all 
the other agents of destruction which surround them. Among works di- 
rectly accomplished by mammals, those which last the longest, and may 
exercise a real influence on the topography of a district, or even its local 
climate, are the structures made by the beaver: rivulets kept back by 
these dams are changed into marshes, or perhaps take a different course, 
and sometimes even become tributaries of another basin. At the time 
when the forests of .Western America were still inhabited by vast tribes 
of beavers, a large number of water-courses were thus changed, by the 
trunks of fallen trees, into a succession of pools. Even in our time, near- 
ly all the streams which flow to the east of the mountains, of British Co- 
lumbia have been dammed up and changed into marshes. The beavers 
have themselves destroyed the water-courses which were necessary to 
their existence.* The worm disturbs the ground to more purpose, for al 
though the work done by each individual may amount to very little, the 
result of the collective labor is nevertheless of the greatest importance ; 
for, as Darwin points out, it is the earth-worm which most contributes to- 
ward preparing the vegetable soil on which we till. 

In the enormous geological changes caused by animal life, the creatures 
themselves have taken no voluntary part; and if they modify the face of 
the planet, it is solely owing to the accumulation of their debris. The 
humble sphagnum, and other marsh plants, owing to their innumerable 
multitude, ultimately spread thick layers of peat over vast plains and 
even on mountain slopes, and in the same way the very smallest animal- 
culae, multiplying by myriads and myriads, at length form immense strata 
in the outer crust of the earth. One-quarter of the town of Berlin is built 
on loose soil composed of successive generations of these infinitely tiny 
creatures ; at the mouth of the Oder and many other rivers, in the port 
of Wisraar, and on the bar of Pillau, a third, or even a half, of the mud is 
formed of living species accumulated in incalculable numbers ;f the mass 

* Milton and Cheadle, Voyage de VAtlantique au Pacifique. 

t Rechcrrhes d Ehrenherg en 1839. — Anton von Etzel, die Ofsee. p. 421. 



422 LIFE. 

of animalculae which every century is deposited in the port of Pillau must 
at the very least be estimated at more than a million cubic yards. This 
mud will some day dry up, and, like schist and sandstone, form solid 
strata in the plains and mountains of terra firma. In the same way dia- 
tomacea and forarainifera from the bottom of the ocean,* and corals from 
the superficial strata of the sea, are constantly at work building up geo- 
logical rocks, like those which were formed by species in former ages, and 
at the present time constituting parts of the main-land. By their constant 
work of assimilation, polycistina, globigerinse, sponges, madrepores, and 
other workers of the sea, collect the carbonic acid, lime, and silex brought 
down by the rivers, and rebuild the earth slowly with these materials. 
While water-courses are gradually wearing away the foundations of 
mountains, and demolishing them particle by particle, the inhabitants of 
the sea are engaged in laying the foundations of a new world. Some 
idea may be formed of the immense part played in the history of our 
planet by marine organisms, when we take into consideration the produc- 
tion of the calcareous formations which cover so large a proportion of the 
earth's surface. Burmeister rightly remarked that, whatever may have 
been the origin of limestone, dolomite, and chalk, it is quite certain that 
all the rocks of this mineral composition have been "eaten and digested" 
by animalculae similar to those met with in the ocean at the present time. 
The foraminifera in the bed of the North Atlantic deposit calcareous mat- 
ter exactly like that found in our present mountains ; new oolitic rocks 
are formed composed entirely of small Orbidina universa.\ 

The best known, if not the most active, of these workers of the sea, 
these " world-builders," J are the zoophytes [Zoantharia), numbering some 
hundreds of species, the accumulated debris of which forms vast tracts 
of land in the South Sea and the tropical Atlantic. The corals of more 
temperate zones do not increase in multitudes sufficiently numerous to 
form banks of rock to any great extent. Only those waters of which the 
temperature is at least sixty-six degrees Fahrenheit — that is, within an 
equatorial zone about fifty degrees in breadth — form the scene of opera- 
tion in which these enormous crowds of workmen can live and multiply, 
and, by the elaboration of the calcareous matter contained in solution in 
the body of water, can gradually cause dry land to rise up fi'om the bed 
of the ocean. The working polyps, most of which belong to the madre- 
pore family, can not live in any seas which are crossed by cold currents. 
There is not a single coral reef to be seen all along the western coasts 
of South America, which, although warmed by a tropical sun, are also 
washed by the cool watei's coming from the south pole. The gradual in- 
crease of cold in the deeper strata of the sea is also probably the reason 
why the coral-builders live only at a slight depth below the surface: be- 
low twenty-five fathoms the dredge does not discover a single specimen. 

In certain parts of the South Sea, multitudes of these animated flowers, 

* See above, p. 400. t Nautical Magazine, November, 1862. 

X Michelet, La Mer. 



REGION OF CORAL REEFS. 421^ 

the different varieties of which shine with the mo|t brilliant colors, give 
to the surface of the water in its shallower parts the appearance of a 
field studded with glittering flowers. The color ^f the calcareous masses 
produced by successive generations of madrepores is generally of a dead 
white. The reefs constructed by the meandrines rise up in conical pro- 
tuberances, which are covered with winding lines like the circumvolu- 
tions of a lobe of the brain ; the edifices built by porites spread out in 
large regular strata, while those of other creatures are composed of cavi- 
ties bristling with points, sometimes even assuming the appearance of 
petrified brush-wood. When the reefs have gradually emerged from the 
sea, and have been left by the colonies of animals which inhabited them, 
the different species of coral forming the rocks may often be recognized ; 
but in many cases the stems and branches of coral have been broken into 
so many fragments, and so intimately mixed up with the debris of shell- 
fish, that no trace of the original fabric can be discerned ; the rocky mass, 
which is entirely an animal production, appears quite as destitute of de- 
bris of any regular form as beds of sand. Every trace of the life which 
has produced the islands, and is still at work on their outer edges, has 
completely disappeared. Having undergone this change, the calcareous 
rock, which, moreover, bears an exact resemblance to strata of the same 
origin which were deposited during ancient geological pei'iods, is often 
very compact, and sometimes even partially crystalline, like a sort of 
inarble.* 



^ Fig. 175.— Profile of a Coral Reef (after Darwin). 

In reefs still inhabited by living creatures, the most active corals, such 
as the meandrines and porites, are those which occupy the external por- 
tions of the rocks which are exposed to all the force of the Avaves ; their 
calcareous bulwarks, which break the force of the tides and the surf, pro- 
tect the more delicate species which take shelter in the channels and la- 
gunes inside the reef. The banks are not, however, entirely composed of 
])olyps ; shell-fish abound in great variety in all the little pools among 
the rocks, and augment with their remains the thickness of the mass ; 
echinoderms fill up with their spikes all its crevices ; and, lastly, myriads 
and myriads of foraminifera, forming a lesser world living in this world 
of corals, swarm in every wave which washes the reef. In many pai'ts 
of the South Seas, especially on the great barrier round Australia, the 
sand is entirely composed of whitish disks of these marine animals. All 
this immense swarm of animation, which may be compared to a chemical 
apparatus of vast dimensions, is incessantly engaged in assimilating the 
calcareous salts which have been carried away from the earth by the sea- 
water, and is storing them up for the formation of future continents. 
* Beete Jnkes, School Manual of Geology, p. 67, fF. 



424 



LIFE. 



In spots where the s^ibterranean forces, which are at work in the depths 
of the earth, are upheavhig the bed of the seas, the reefs naturally emerge 
in a period more or les% prolonged acpording to the power which impels 
them, and, during the course of ages, gradually rise above the sea with 
the islands of which they have laid the foundations. Nevertheless, the 
madreporic rocks also ultimately emerge from the water in places where 
a gentle movement of depression is gradually swallowing up the former 
land. Many an island which reared its mountain high above the ocean 
has long since disappeared, and ships now cast anchor in the very place 
where its summit was swallowed up ; but round the former sea-coasts, 




Fig. 1T6.— Koadstead of Papeiti (Island of Tahiti). 

which are at the present time covered by the Avaves, there is now spread^ 
out an annular belt of islets and reefs rising out of the water like a living 
wall; these extraordinary ranges of narrow reefs, disposed in a circular 
or oval form in the middle of the sea, constitute those atolls the forma- 
tion of which has been so well explained by Darwin.* Accoi'ding to 
Dana, the larger coral islands of the Pacific are 290 in number, and to- 
gether comprehend an area of 60,000 square miles — that is, about an 
eighth part of the ground rising above the surface of this ocean. As far 
as the smaller islands of the same origin are concerned, no attempt has 
* See The Earth, the chapter entitled Upheavals and Depressions, 



REGION OF CORAL REEFS. 



425 



yet been made to count them. Tlie king of the Maldives, a name signi- 
fying " innumerable islandf^,''^ can, without any exaggeration, assume the 
title of Sultan of thirty atolls and 11,000 islands.* 



r 



/ 




till 
f 



f.# 



V 




Fig. 177.— Gambler Island. 

Since 1702, when Strahan discovered the marvelous productions of the 
madrepores, every navigator tells us how the structures brought up by 
the polyps to the level of the water may gradually be converted into dry 
land, and become covered with vegetation. The waves break in pieces 
the projecting stems, and, lifting up the looser fragments of coral, drive 
them onward to the highest point of the reef There, by degrees, they 
form a bank of debris on which the breakers beat, and bring from the 
open sea sand, broken shells, and the remains of the innumerable organ- 
isms which swarrii in the ocean. Enriched by these additions brought to 
them by the waves, the calcareous bank becomes covered here and there 
with a tliin layer of vegetable soil, ^Yhere, sooner or later, some seed ger- 
* Dana, United States Expedition. 



426 



LIFE. 



minates which has been carried away by the current as it washed the 
coast of some distant land. A few land plants embellish with their verd- 
ure the gray and monotonous coast ; after a time trees take root there ; 
then insects and worms, carried along on drift-wood as if on rafts, begin 
to populate the incipient groves ; birds resort thither, to hide their nests 
among the foliage; and at last it often happens that some fishing-party, 



&^^<S\^vv\^SS^,V\^\-^ - 



^ vv\^SSS^i^x\i ^^^C.^ v^v-vv-.\vSiS&:$SSS: 



Pig. 178.— Profile of Gambler Island. 



attracted from afar by the beauty of the site, come and take possession of 
the new land, and build their huts on the edge of a spring which had been 
gradually formed in some cavity by the subterranean filtering of the rain- 
water. Such has been the history of hundreds and thousands of the isl- 
ands scattered over the Pacific Ocean and the Indian Sea. Some of them 




Fig. 179.— Atoll of Menchikoff. 

have been known to take their rise during the course of the present cen- 
tury. Thus the island of Bikri, in the atoll of Ebon, had not reached the 
surface of the water in 1825; but in 1860 it had alrea'dy become a dry 
rock, with an area of about four roods, and some pandanus, sown there 
by the waves, were growing in the sand on the shore. Other islands, for- 
merly separated from each other, are now united so as to form a crescent- 



FRINOINO REEFS. 427 

shaped tract of land, and the former divisions may still bo recognized by 
their rocks, which are either bare or covered with a scanty vegetation.* 

Generally speaking, the section of the ring which is turned toward the 
point of the compass whence the wind most frequently blows is that which 
presents the greatest extent of dry ground, or even a complete half circle, 
for the animalcula? building the reef take a delight in the beating of the 
surf There are, however, certain archipelagoes, like that of the Marshall 
Isles, where islands continuously increase on the very side of the atoll 
which is least beaten by the waves. This fact is accounted for by the 
violence of the north-east trade-wind, which, during six months in the 
year, carries from the eastern to the western reefs all the broken pieces 
and drifting matter, and thus constructs an artificial bank on the least 
populated side of the atoll. 




ll»35- ...-- 






Fig. 180. — Brown's Archipelago. 

Still, the appearance of reefs differs considerably according to the activ- 
ity of the coral insects, and the various physical conditions of the ground 
on which they erect their structures. All round a great number of isl- 
ands,! Tahiti being an example of this class, the reefs of madrepores 
fringe the shores like the shoals on the rocky coasts of Brittany, and be- 
tween terra firma and the belt of reefs properly so called there is little 
more than a narrow canal, through which vessels make their way with 
difficulty ; but being protected against the surf of the open sea, they are 

* Doane, American Journal of Science and Arts, May, 18G0. 
t See Fig. 176. ' 



428 



LIFE. 



navigated in safety. Other islands, Gambier* and Yanikaro, for instance, 
are encircled at some little distance by an almost complete belt of rocks 
of a tolerably regular formation. In these cases, however, the central isle 
has disappeared, and its place is taken by a lagune which is surrounded on 
all sides by the atoll with a circle of reefs and breakers. Some atolls are 



ip-lP^. J!<r 



iMai 



APIA 






Pig. ISl.— Part of the Kingsmill Group (after Dana). 

single, like the famous Keeling atoll, which has become celebrated through 
Darwin's description ; others are double, like that of Menchikoff; others, 
again, are multiple, innumerable, so to speak, like those marvelous agglom- 
erations of the Maldives, where each reef is an atoll in miniature, and, 
with other reefs of similar shape, constitutes a larger atoll ; and this larger 

*-See Fig. 177. 



SCATTERED ISLETS. 



429 



atoll is but a link in the immense chain of an atoll having a circumference 
of sixty-two miles.* We also find in the sea many g-roups of scattered isl- 
ets, which do not seem to difler from the dispersed archipelagoes of seas 




Fig. 182.— The Ked Sea and its Coral Keefe. 



in the temperate zone, and would not be recognized as fragments of some 

large anuular islands, were it not that a circle of shallow water shows that 

* Sec The Earth, the plate representing the Atoll- Ari. 



430 



LIFE. 



these islets are nothing but the emerged points of a submarine atoll. As 
an example of this formation,' we may mention " Brown's Archipelago." 
Lastly, certain coral islands, especially those in a certain part of the Kings- 
mill archipelago, assume the shapes of almost perfectly regular triangles 
and Squares. It is difficult to explain this strange arrangement, whicli 
doubtless proceeds from the collision of oceanic currents. 




Pig. 183.— The Keys of Florida. 

By comparing on several occasions the exact height of the coral reefs 
situated at the foot of the forts on the rocks of the coast of Florida, Agas- 
siz found that the average growth must be computed at from seven to 
eleven inches in a century. Thus the madrepores appear to take a long 
time over their work, and very small changes in the comparative distri- 
bution of land and sea occupy a long succession of ages in their accom- 
plishment; nevertheless, these innumerable multitudes of animals, engaged 
as they are in the incessant construction of their calcareous edifices, are 
of the greatest importance in the history of the world. They are at work 
on almost all the shallows and coasts of the Red Sea, the Pacific, and the 
Indian Ocean — that is to say, on a total extent of coast-line of several 
hundreds of thousands of miles. It is not, therefore, a mere figure of 
speech when geographers designate corals as the buildei-s up of future 
continents. Between Australia and New Guinea, in that part of the ocean 
which has received the special name of " the Coral Sea," countless myri- 
ads of coral insects are employed in concert in no less a work than the re- 
construction of that sunken portion of the world which in the southern 
hemisphere once tended to balance the miglity mass of Asia. The con- 



Tlie Oceau,&c 



THE GREAT BARRIER REEFS 
j4ND the straits of TORRES. 



PL.XXl 



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BARRIER REEFH. 



431 



tinuous line of reefs which stretches outside the coasts of Queensland and 
the peninsula of Cape York is not less than 931 miles in lengtli ; toward 
the entrance of Torres Straits, this coral wall, appropriately named the 
Great Barrier^ is changed into a regular dike, the openings of which are 
known only to the cleverest sailors. For a space of about 310 miles, any 
access to the coast of xlustralia and the Straits of Torres is completely 
shut out by this winding rampart of madreporic rocks ; and beyond this 
obstacle ships sailing toward the Sunda Isles have still a number of reefs, 
to round ; there is also a complete labyrinth of narrow canals which must 
be carefully followed ere they reach the open sea. We might justly say 
that an isthmus of rocks, 124 miles in breadth, has almost united the Aus- 
tralian continent to the large island of New Guinea. 



■;S_ 




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Fig. 184.— The Bahama Archipelago. 

In the Atlantic Ocean, the only coral structures of any importance are 
to be found at the outlet of the Gulf of Mexico. The Peninsula of Flor- 
ida, a low and marshy tract of country in which the only hills are merely 
mounds of sand raised by the wind, is entirely composed of coral debris 
and calcareous sand. This enormous territory, not less than 78,000 square 
miles in extent, reckoning up to the line where the continental highlands 
begin, is the work of polyps. Taking for the foundation of their edifices 
a long strip of sand, Avhich was probably formed between the waters of 
the Gulf Stream and those of the main sea, the animalcula?, in the first 



432 



LIFE. 



jDlace^built their structures up to the water's edge ; the waves have after- 
ward destroyed all these reefs, and havmg reduced them to sand, cement- 
ed them into one solid mass in combinatiQn with all the debris cast up by 
the sea,* It must, however, be confessed that the corals have taken their 
time over this immense undertaking. According to T. Sterry Hunt, the 
period which the polyps must have required for raising the reefs of Flor- 
ida from east to west would be at least 864,000 years, and the develop- 
•ment of the peninsula from north to south must necessarily have occupied 
a period of not less than 5,400,000 years.f Florida has now ceased to in- 
crease toward the east ; for on this side its shores are bordered by the 
deep water of the Gulf Stream, and polyps, as they work only in shallow 
water, can not live there. The peninsula increases in extent only on its 
western and southern coasts. 




Fig. 185.— Cross-section of the Bahama Islands. 



As has been shown by the explorations of Agassiz and several officers 
of the American navy, the construction of the southern point of Florida 
presents the remarkable phenomenon of concentric coasts, A long way 
out in the sea, and even on the very edge of the bed which is filled by 
the waters of the Gulf Stream before they make their way through the 
Bahama Channel, there extends a semicircular range of rocks, which here 
and there reach the surface of the water, and along almost their whole 
extent are still in course of construction ; this is the future coast of the 
peninsula. Inside this first range of reefs, which is only indicated by 
breakers and a few rocks, there extends a long curve oi keys or cayos, 
composed of islands, islets, and rocks, forming an almost continuous line; 
this constitutes the true coast of the peninsula, and on its extreme point 
has been erected, as if to keep watch, the great fort of Key West, one of 
the most important military depots and maritime and commercial stations 

* Agassiz, Coast-survey Report, 1861, 

+ Silliman's American Journal, March, 1864, 



CORAL ISLANDS. 



433 



in the world. Behind this sheltering range of keys, at an average dis- 
tance of nine miles, stretches out the regular coast, composed, like the ex- 
ternal reefs, of coralline debris ; then, farther inland, the geologist finds 
again ancient banks, and separated from each other by marshes and tracts 
of low lands ; these were the reefs which two or three hundred centuries 
ago were beaten by the waves, at an epoch when the present coast was 
notliing more than a succession of islets scarcely level with the water. 



depth) vvyard^ 







Fig. 186 The Islands of Eleuthera and New Providence. 

The Bahama Islands, which are also structures erected by coral insects 
in the shallow parts of the sea, present, like Florida, a sort of fa9ade which 
at the east is suddenly cut off by the depths of the open sea; the western 
side, in the still waters of the great banks, is the spot where the organic 
debris and mud accumulate, which sooner or later will form the largest 
archipelago in the West Indies. On the side toward the main sea the 
islands are developed into a very elongated arc of a circle, and uniformly 
present the appearance of incomplete atolls; madrepores, astreas, and car- 
yophyllffi, which delight in working when washed by the huge waves of 
the open sea, can not, in fact, complete their structures except upon the 
side which is washed by the surf, and therefore do not build annular walls 
like those which rise amidst the waters of the Pacific. 

28 



434 LIFE, 



BOOK III.— EARTH AND MAK 



CHAPTER XIV. 

THE INFLUENCE OF NATURE ON THE DESTINY OF MANKIND. — ANTIQUITY 

OF THE HUMAN RACE ON THE EARTH. MONOGENISTS AND POLYGE- 

NISTS. FUSION OF HUMAN RACES. 

Man does not only live upon the surface of the soil, he has also sprung 
from it ; he is its son, as we learn from the mythologies of all the nations. 
We are of the dust, the water, and organized air; and whether we may 
have sprung from the slime of the Nile, whether we may have been form- 
ed from the red earth of the Euphrates or the sacred alluvium of the Gan- 
ges, we are none the less the children of the "beneficent mother," like the 
trees of the forest and the reeds of the rivers. She it is from whom we 
derive our substance ; she nourishes us with her mother's milk, she fur- 
nishes air to our lungs, and, in fact, supplies us with that wherein " we 
live, move, and have our being."- It must, therefore, ne(?essarily be the 
case that those special forms of the earth with which their flora and fauna 
harmonize so wonderfully should be likewise reflected in "the vital phe- 
nomena of that one fauna which we call mankind. 

All the organisms which exist on the surface of the earth may, it is 
true, act in opposition to nature, and infringe the limit fixed by the vari- 
ous climates they have .been used to according to the intensity of their 
vital energy. Plants and animals are ever seeking to enlarge their do- 
main, and, species by species, carry on an incessant struggle for the pos- 
session of the soil. Owing to their vital energy, the more energetic tribes 
shift their possession, and become difi"used over vast countries, where the 
geological and climatic conditions are exceedingly varied; but as they 
pass the boundai'ies of their native habitat, the types die away, or become 
modified under the influence of the new surroundings. The harmony be- 
tween the earth and its products is thus disturbed, but only to be gradu- 
ally re-established, in conformity with the laws which govern all planetary 
phenomena. But in thus exercising their own peculiar energy so far as 
is consistent with the conditions of their life, the special faunas an(f floras 
only add to the wonderful harmony of the earth, and of all that springs 
up and grows upon its surface. 

Man, the "reasonable being" who so much delights in boasting of his 
free-will, is nevertheless unable to render himself independent of the cli- 
mates and physical conditions of the country which he inhabits. Our lib- 
erty, in our relations with the laud we live in, consists in recognizing its 



INFLUENCE OF NATURE ON MAN. 



435 



]a\vs, in order that we may live in accordance with them. However great 
may be the comparative facility of life and action which we have gained 
for ourselves by our intelligence and personal volition, we none the less 
remain mere products of the planet ; fixed to its surface like imperceptible 
animalculjB, we are carried along by all its movements, and are dependent 
on all its laws. Moreover, we do not belong to the earth tuerely as isola- 
ted individuals ; for associations of men, taken as a whole, must, at their 
origin, have necessarily been raoraed into shape on the earth on which 
they took their rise ; in their inner organization they have been compelled 
to reflect the innumerable phenomena of the continental outline, their riv- 
ers and sea-coasts, and their circumjacent atmosphere. All the primitive 
facts of history are explained by the disposition of the geographical thea- 
tre on which they have taken place ; we have even a right to assert that 
the history of the development of mankind has been written beforehand 
in sublime lettering on the plains, valleys, and coasts of our continents. 

A geometrical parallelism is not, however, the point in question here. 
The resemblance between facts and the scenes that surround them is not 
an absolute one, as would be the image of an object reflected in a looking- 
glass. No, the accordance which exists between the globe and its inhab- 
itants is composed both of analogies and contrasts; like all the harmonies 
to be perceived in organized bodies, it proceeds from conflict as much as 
from concord, and never ceases to oscillate round a shifting centre of 
gravity. The forces at work both on the surface and in the heart of the 
earth ai'e always in action, and geological phenomena bear witness to this 
fact. In the same way man is incessantly engaged in a conflict with the 
globe on which be dwells. Having submitted to be a child of nature 
during the ages of i^rimitive barbarism, he has gradually emancipated 
himself, and now endeavoring to adapt to his use the forces of the earth, 
he has, so to speak, made them his own. The action of the planet on 
man, and the reaction of man on the planet, are the agencies which have 
given rise to that harmony which forms the history of the human race. 
These ficts, however, have become little more than truisms since the 
Humboldts, the Ritters, and the Guyots have, by their labors, establish- 
ed the Solidarity which exists between man and the earth. When the il- 
lustrious author of the " Erdkunde " compiled, by his unassisted efibrts, 
his great encyclopaedia, the grandest geographic monument of ages, the 
leading idea which inspired him wa| that the earth is the body of man- 
kind, and man is the soul of the earth. Without thus proudly appropria- 
ting to ourselves the globe on which we tread, we are still justified in as- 
serting that though for a long time we were nothing more than its uncon- 
scious products, we have become increasingly active agents in its history. 

It is now proved that man has existed on the earth since a very remote 
period. Written documents do not carry us back farther than thirty or 
forty centuries ; the most ancient remains of edifices built at any previ- 
ous epoch, which also may be called archives of stone, date back perhaps 
two thousand years before; but far beyond this short historic period, 



.436 . LIFE. 

which scarcely comprises the lapse of one hundred and fifty generations, 
extends a space of time, certainly much longer, known to us only by pure 
tradition. Then mankind, rising to a moi'e enlarged self-consciousness, 
linked age to age by legends, poems, and symbolic formula ; the reminis- 
cences of great events, migrations, wars of race's, alliances, exterminations, 
and triumphs of industry, were incorporated into religion itself, and, in an 
increasingly varied form, were handed down from age to age as the herit- 
age of nations. In still more ancient #mes, in the dim mist of by-gone 
ages, our ancestors lived the life of wild beasts in forests and caves. Tra- 
dition, no less than history, is dumb as to this epoch of the human race ; 
but the strata of the earth, explored in our time by geologists, are begin- 
ning to reveal to us both the existence and the customs of these ancestors 
of ours long unknown to us. 

To say nothing of the objects discovered at various ej^ochs at a time 
when science, still timid, refused to recognize the antiquity of man, so 
many human remains and so many productions of primitive industry have 
been lately met with, that, comparatively speaking, there can no longer 
be any doubt as to the long duration of our species. Not only did our 
ancestors inhabit forests contemporaneously with the Bos urics, now ban- 
ished into the Caucasus, and in Europe represented in a few parks by one 
or two specimens ; but anterior to this epoch they also existed during the 
glacial period, at a time when France and Germany presented the aspect 
now oifered by Scandinavia, and the reindeer, now banished to the vicin- 
ity of thfe northern zone, frequented the glaciers of the Alps and the Pyr- 
enees. At a still more ancient period, at an epoch when the European 
climate, which must subsequently have become so much cooler, was, on 
the contrary, much warmer than in the present time, the cave-men had 
for their contemporaries certain species of rhinoceros and elephants which 
are now extinct, and even then artists, humble predecessors of Phidias 
and Raphael, endeavored to carve representations of mammoths upon 
their implements which have been preserved in the earth of caves. Be- 
fore this ej)och man still existed, striving for mastery against a formida- 
ble enemy, the great cave-bear, representations of which he likewise left 
engraved on stone ; and still farther back, in the dim mist of ages, we 
learn from other remains— those of the jEJlephas antiquus and meridionalis 
— that our ancestors were already in being during a period whose life 
was once believed to have been separ^g^ed from the present era by a succes- 
sion of sudden cataclysms. How many thousands or even millions of years 
have elapsed since that time ? This question as yet no one can answer.* 

The shape of the skull shows that the human remains found at Eyzies, 
near the border of Dordogne, must have belonged to a race which even 
now might be reckoned among the most beautiful of its kind : the skulls 
found by M. Garrigou in the caves of Ariege, and perhaps belonging to 
people of the historic epoch, are of very noble proportions; but the skulls 
found at Engis, in Belgium, Neanderthal, in Rhenish Prussia, Borreby, in 
* Boucher de Perthes, Lartet, Christie, Lyell, Lubbock, Garrigou, Broca, etc. 



ANTIQUITY OF ^lAX. 437 

Denmark, and Eguisheim, in Alsace, prove that numbers of the primitive 
inhabitants of Western Europe were very much inferior to the civilized 
people of our days. Though perhaps more agile in pursuing their prey, 
and more powerful in bringing it to the ground, these representatives of 
extinct races were less intelligent and had less of the man about them 
than we, and their facial angle bore some approach to that of the wild 
beasts Avith which they were compelled to struggle for very existence. 
As Professor Huxley remarks, the difference in capacity between the sf ull 
of civilized man and that of the man of Neanderthal or Borreby much 
exceeds the difference which exists between ancient human skulls and 
those of the largest-sized monkeys. Must Ave therefore conclude, with 
Carl Vogt and many other anthropologists, that man is descended from 
one or several species of these quadrumania, which have gradually devel- 
oped by the process of selection, or through a contest for life extending 
throughout a long lapse of ages ? Wl have here a theory which, far from 
being humiliating to mankind, should, on the contrary, be a source of 
pride ; our own immense progress would justify a very considerable ex- 
pectation on this point. Nevertheless, although it is all very well to set 
up and discuss these grave hypotheses, we must, however, be on our guard 
against accepting them as demonstrated facts as long as*no direct evi-* 
dence has been definitely brought forward. 

Since we are necessarily still in doubt as to the very origin of mankind, 
it is obviously impossible to ascertain whether the different races of the 
earth are descended from one couple, or from several primitive groups. 
Is it a fact that all men, black and white, red and copper-colored, own the 
same Adam as their pi'ogenitor, and the same Eve as their common moth- 
er ? Or has each continent, each isolated tract of land, produced autoch- 
thonous races distinct from every other, as it had previously produced its 
peculiar flora and fauna? Although this question is as yet insoluble, 
none is more discussed by anthropologists. Some maintain that the prim- 
itive unity of the race is an indisputable fact, and that it could not be de- 
nied without making a kind of attack against the majesty of mankind; 
others are of opinion that there were three, four, five, ten, or eleven primi- 
tive groups ; there are some, also, who talk of hundreds of various races 
which have sprung up here and there, at different epochs, on continents 
and islands, like the plants, the seeds of which were sown, so to speak, at 
random. In support of this theory, they cite the well-known fact that 
the types of fossil man in Western Europe present contrasts much more 
striking than those observed in the races of our time. 

Moreover, the passio^ns of our nature, having no alliance with science, 
have been mixed up in this debate. At the time Avhen the American Re- 
public was still unfortunate enough to reckon along with its thirty mill- 
ions of white men, the freest in the universe, four millions of negroes con- 
demned to the most degrading slavery, both polygenists and monogenists 
used to dispute d outrance in scientific language ; they went so far as to 
invent arguments, not to establish the truth, but either to justify or to 



438 . LIFK 

curse slavery. Even among those who believed in the tradition of the 
primitive unity of the human race, many asserted, out of hatred to the 
blacks, that this unity has been broken during the course of ages, and 
that the children of slavery were forever doomed to the lash and to the 
iron collar. These contests, provoked by the strife of interest and feel- 
ings, have not resulted in any scientific certainty, and the origin of our 
race remains as obscure as ever. This ignorance is naively illustrated by 
m«st of the myths which recount how the life of the first men began by 
sleep. "ISTothing was in being," say the old men of an Indian tribe; 
" all was null and void. There was no sky, no earth, no sea, no shore. 
Suddenly seven warriors found themselves seated on the edge of a lake, 
smoking the calumet of peace, and their wives were already working in 
the wigwams." No legend brings more vividly before us that man passed 
his infancy as if in a dream ; his first commencement was living without 
knowing it. • 

It matters, moreover, but little whether man is descended from one or 
several primitive couples of ancestors 5 it is of little importance whether 
races so diverse in their nature were all begotten by the same family, or 
whether they were born in difierent countries and at difl:erent epochs, 
■provided that* this unity, though doubtful in the past, becomes a matter 
of certainty in the future? This is one of those great questions which 
anthropologists are now putting to themselves, and we believe that it 
will be very near its solution when the results shown by experience are 
adhered to in good faith. According to some savants, various races can 
not blend one with the other; the black can not permanently unite with 
the white man ; the Red-skin, the South Sea islander, the Arab, and even 
the Chinese, can never enter the great family of their brother nations ; 
and more than this, the Hindoo, althongh no less Aryan in his origin than 
the Western European, and actually his precursor in arts and sciences, is 
compelled to remain excluded from the circle of the proud Celtic and 
Germanic races, without renewing the former bonds of parentage. Ac- 
cording to this theory, which is absolutely enunciated by some, and more 
or less softened down by others, the progeny of any union between diff^-- 
ent races would be a family of hybrids, destined either to die away from 
sterility, or to produce successive generations the special type of which, 
growing weaker and weaker, could only ultimately result in the repro- 
duction of one of the two original races. And even a more melancholy 
fact ! Certain inferior tribes, altogether incapable of uniting with the 
masters of the earth, or even of living in the same civilized state, will 
have no alternative left but to die out — the earth not being large enough 
for them and for the men of the victorious race ! 

Alas ! the self-styled civilized man has often proved his superiority 
over other races by a merciless course of destruction ; he has hunted 
them do^yn like game, sometimes in order to seize their land, their jewels, 
or their arms, sometimes to make slaves of them, and sometimes merely 
for tasting the pleasures of wholesale slaughter. The number of victims 



ANCIENT AND MODERN TYPES. 439 

wliich have been thus sacrificed during the last four centuries must be 
computed by millions and millions, and whole tribes, and even nations, 
have completely disappeared. It may be easily understood that, in the 
face of this immense massacre, the fusion of races could not be effected. 
Nevertheless, if the greater part of Europeans, instead of showing them- 
selves to be mere exterminators, and clearing away all before them, had 
been somewhat less of barbarians, if they had adhered to the plan of 
evincing their native generosity by coming forward as friends, and as be- 
nevolent and just individuals, can we believe that they would have failed 
in coming to a good understanding with the natives, and that a union 
would not have been easy between the distinct races ? In every part of 
the world, the common understanding of what is just and right would 
have marvelously facilitated the alliance. If it is a fact that fusions be- 
.tween different races can produce nothing more than sterile hybrids, the 
case is plain : mankind is condemned to death — and to a rapid death — 
for peoples and races are every day more and more mixed up, the front- 
iers of countries are disappearing, and by cross-breeding upon cross- 
breeding all men will ultimately become one and the same family. 

In spite of the terrible conflicts which have taken place, in spite of ex- 
terminations,, and in spite of slavery, the whole of South America, the re- 
publics of Central America, the West Indies, and a portion of the United 
States, are now peopled with a mixed race, i» which blacks, whites, and 
red-skins are found blended together. Is not that part of the earth which 
we call the New World inhabited by newly-formed peoples, the type of 
which is in no way confused with that of either of the races which pro- 
duced it, but is all its own ? Is it ^ot a fact that all these populations, 
which resemble the European in intelligence and ideas, the Indian in an 
indomitable spirit of stubbornness, and the African in his enthusiasm and 
gentle qualities, are living proofs that the various human races might 
easily be united into one, in spite of the difference in their origin. Sub- 
jected to the influences of rapid changes, journeys without end, the vari- 
ous elements brought in by emigration, the intermixtures between fami- 
lies, the modification of climates produced by cultivation — the types of 
mankind, becoming more and more mobile, blend and ultimately unite : 
if these types in former days remained unchanged, the cause was the im- 
mobility of nations. The Esfyptian of our time, although characterized 
by slight modifications pointed out by Brugsch, is much the same as the 
figures which we see enslaved and bent down on the fronts of obelisks 
and on the pedestals of statues. But there is no painting, there is no de- 
sign engraved either on stone or metal, which has ever given us any indi- 
cation of the type of the modern North American, or Yankee, or of the 
Spanish-American. 



440 ' LIFE. 



CHAPTER XV. 

INFLUENCE OP CLIMATE. — TEOPICAL ZONE. — FRIGID ZONE. — TEMPERATE 

ZONE. 

The various conditions and surroundings regulating climate are so ex- 
tremely divei'se in different parts of the world, it is only possible, in the 
most general way, to point out their influence on the inhabitants. Thus, 
in the tropical zone, there is a complete contrast between deserts desti- 
tute of water and verdure, and the luxuriant lands on which at one time 
the sun shoots forth its flame-like rays, and at another the clouds pour, 
down their showers in cataracts. 

The development of life is rapid in climates where the winter season 
follows immediately upon tropical heat. It advances with rapid strides, 
and death also hastens on behind it ; gigantic trees inhale currents of car- 
bonic acid through their thirsty leaves, and absorb them into their nu- 
merous tissues : bamboos may almost be seen to grow, and marshes are 
concealed under isles of floating herbage. No sooner does a storm over- 
throw the mighty giants of the forest, than fresh vegetation springs forth 
from the shattered bark. Thus life, ever indefatigable, causes multitudes 
of new organisms to shoot out from the death of the old. In this fruitful 
climate, where the air is pervaded with heat and saturated with moisture, 
^ those vegetables which are used for the food of man grow in the greatest 
abundance. In many regions of the tropical zone, all that man has to do 
whjen in search of food is to shake the branches of the trees, or pull up 
roots from the ground. His needs are so very few, and life is so easy 
to him, that he cares little about it ; he is not compelled to sustain it 
by dint of work, but it meets him, as it were, half way, and he almost 
despises it, because its favors are so generously offered. He therefore 
meets death without a regret, and not one tear is shed when he closes 
his eyes forever. Sudden epidemics visit the inhabitants, as storm-clouds 
beat upon a forest ; sometimes even famine carries away whole popula- 
tions, who have not been wise enough to store up the resources offered 
to them by nature against future times of want. But what matters the 
death of a man, or even that of whole ti'ibes ? Children innumerable 
take the place of those who have departed, and grow up like the grass in 
a newly-mown meadow. Thus the mildness of the climate, the fertility 
of the soil, the exuberance of life, and the suddenness of death, take an 
equal part in maintaining man in his native carelessness and idleness. 
Taken as a religious being, all he can do is to bend in silence before the 
majesty of mighty nature. Her violence is too terrible, her energies are 
too impetuous, the great alternations of her actions ai'e too regular, for, 
the feeble being placed in her midst to be any thing but her slave. He 



INFLUENCE OF CLIMATE. 44I 

will worship her in all her phenomena : in the rays of the sun, because 
they burn anci destroy ; in the clouds, because they peal forth thunders ; 
in the dai'k forest, because serpents and tigers are hidden in its depths ; 
in .all tliat surrounds him, because every thing lives with an irresistible 
force of life which may at any time cause his death. The stupendous 
work which is unceasingly going on around him hinders any personal 
labor; he thinks but little; when, like the Hindoo, he meditates and con- 
templates the laws of nature, his ideas somewhat tend to the jirofound 
and the immutable, like the laws of which they are the reflection. 

The rich nature of the tropics, even on account of that richness, is, as we 
see, not the most favorable to the progress of mankind, but the frigid zone 
is still less fitted to be the residence of prosperous nations. But a few 
ti-ibes have wandered into the solitudes of these countries, where they 
have struggled painfully with the climate, in order to extort from it each 
day enough to keep up a miserable existence. As, on account of glaciers 
and the absence of vegetation, they can not peneti'ate far into the interior 
of the islands and continents'on which they live, they build their wood or 
snow huts on the sea-shore. There, at least, the wind now and then wafts 
to them a few gusts of equatorial air, there the counter-currents drive 
upon the shore water which has come from the tropics, and still retains 
something of its primitive warmth ; and when the sea is not too stormy, 
or too much covered with drifting icebergs, the fisherman is able to ven- 
ture out in his leathern boat in quest of seals and fish. "When he has 
pierced with his harpoon the animals which are to serve as food for his 
family, he returns to the small black hole which forms his miserable re- 
treat, where, warming himself by the flame of a lamp, he spends the 
long winter night, which seems as if it would never end ; for even the 
sun, the source of heat for all terrestrial life, abandons the frigid zone for 
whole weeks and months, while the aurora, which at intervals takes its 
place, sheds but a livid gleam, a mere phantom of the day. Existence is 
a difficult matter during this long and gloomy winter; famine, too, often 
makes great havoc among these people, and sometimes whole tribes have 
disappeared without leaving a trace behind them. How could it be oth- 
erwise than that the mind of the Greenlander, the Esquimaux, and the 
Kamtchadale should sufiTer under the influence of the desolate climate of 
the polar regions ? All travelers relate that the most simple pleasures 
are suflicient to fill up the 'cup of joy for artless beings like these, whose 
■ life is always so monotonous; in their struggle for existence, ambition 
does not form a part ; for the main point with .them is to procure food, 
and the soil is too ill adapted for cultivation, and the climate is too inclem- 
ent for them to be able to counteract the difficulties presented by the 
land, and to make any endeavor to appi'opriate it for their own use. 
They are loving and gentle in disposition, for a family living together 
as they do in their snow hut must be all the world to each other; they 
are attached to their native land, and die when obliged to leave it, be- 
cause their ideas are as unsophisticated as the country in which they 



442 LIFK 

were bom, and there only can they experience the simple pleasures and 
peaceful joys which refresh them after their labors. Even among nations 
there are some that are always children, and they perish when they are 
torn away from their mother's breast. 

The two temperate zones, and particularly that in the northern hemi- 
sphere, are the portions of the planetary surface which have been the 
most favored in the development of the human race ; and when the more 
or less civilized nations of Western Europe and North America proudly 
attribute to their inherent virtues the great progress attained by them, 
they little know how much is OMang to the favorable climate which has 
assisted their efforts. 

The distinctive characteristic of the temperate zone is the equal and 
periodical alternation of the hot and cold seasons. In the tropics the 
mean temperature varies but slightly, and in the frigid zone intense cold 
yields to a milder climate for only a few weeks during a very shoi^ sum- 
mer; but in the tract of land included between the two extreme zones 
heat and cold follow each other regularly, so as to form two well-defined 
seasons following the path of the sun on the ecliptic. The nations of the 
temperate zones'are reared in a powerful climatic tide, the flow of which 
rises from the equator toward the poles during spring and summer, the 
ebb descending from the poles toward the equator during the autumn and 
winter. The extremes of temperature are always separated by long inter- 
vals of weeks and months, and the influence of contrary climates is only 
shown by successive gradations. In the temperate zone, nature wears al- 
ternately a joyful and a melancholy aspect. During the warm season the 
earth is gay with smiles ; covered with flowers and foliage, it fills the air 
with its perfume, and abundantly absorbs the rays of heat, light, and life, 
which the sun sends down to it. In winter-time nearly all that is green 
seems to have faded ; the delicate outline of the bare branches on the 
trees stands out in relief against the sky, and the ground is often covered 
with snow, as if to shield it from the outer air, and in silence and retire- 
ment to prepare for the germs of life which will bud forth in the spring. 

This succession of seasons does not, however, take place so abruptly as 
to bring about any injury to the organism of man. Months, weeks, and 
days follow their course in the circle of the year with a harmonious and 
measured step, and man, borne along by the seasons, must involuntarily 
be carried along by their movement. During the course of a year he 
passes through climates of the most various nature, and, gazing on a land- 
scape which is ever changing, he alternately sees nature like that in the 
tropics and that in the poles fluctuating around him. The scenes which 
follow one another season after season represent both to his body and 
mind journeys of many hundreds of miles ; he is, so to speak, constantly 
changing his habitat on the surface of the globe. Nature is exhibited to 
him in all the beauty she wears in every climate, without presenting to 
him, except but rarely, the fearful aspect she presents in the zone of hur- 
ricanes and that of boundless snows. 



LOCAL DISTRIBUTION OP MAN. 



443 



The variety of climatic phenomena, and the quiet way in which they 
follow one another, have made the temperate zone the best climate for 
the human race. The life of man is developed better than anywhere else 
in these regions, where the action of naxure is produced energetically and 




Fig. 187.— Density of the Population in Belgium. 

regularly, and the forces proceeding from the equator and those proceed- 
ing from the poles mingle with each other, increasing by their combina- 
tion the number of their phenomena, and yet, notwithstanding, mutually 



23 24 




Fig. 188.— Density of the Population in Greece. 



diminishing the violence of their action. In consequence of the regular 
oscillation of their zone of contact, these forces bring about at the same 
time a condition of movement and equilibrium ; man, to whom they ha^v^e 
given the breath of life, may, by contemplating their alternations, per- 



444 ■ LIFM 

ceive the immuta'ble eternity of the laws which guide them, and the ever- 
varying appearance of the facts which spring from them. A still more 
important fact is, that man is constantly incited to labor ; for, notwith- 
standing the beneficence of nature in these temperate regions, it is only 
shown in moderation, and to those who study and understand her. In 
the spring the ground must be cultivated in prospect of winter, and each 
season must be made a preparation for that which follows. Confident in 
the bounty of the earth, the laborer learns to deprive himself of a part of 
the grain which forms his very existence, knowing that some day he will 
gather a harvest from it ; by incessant and successful efibrts he acquires 
shrewdness, knowledge, cheerfulness, and love of life. 

Therefore, in all the countries of the teijiperate zone which are blessed 
with a fertile, well-watered, healthy soil, and are provided with easy chan- 
nels of communication, there has always been a numerous and increasing 
population, in spite of the wars, massacres, and invasions to which rival 
ambition has so often given rise. As far as Asia is concerned, the central 
part of the temperate region is the locality where we find that " rich cen- 
tral flower " which by itself comprehends more than a quarter of the hu- 
man race ; at the other extremity of the Old World, it is also toward the 
middle of the same zone — in Belgium, England, and Northern France — 
that we find swarms of men living in the closest pi'oximity to one anoth- 
er. Belgium is the country which has the largest population as com- 
pared to the whole world, and contains more than one inhabitant to each 
acre, or at least a quantity twenty times greater than the rest of the con- 
tinent. Greece, which is one of the least populous countries of temperate 
Europe, is, however, in proportion three times more thickly populated 
than the whole of the dry land of the earth, taken as a whole. The com- 
parative populations of the two countries may be imagined from the two 
preceding maps, in which, according to a somewhat difierent system to 
that of M. Minard, the density of the inhabitants for an equal surface is 
made proportional to the number of squares. The space of 2050 miles in 
width comprehended between the 25th and 26th degree north latitude, 
which is not even a third of the continental surface, contains two-thirds 
of the population of the globe, and this is the tract of country where, in 
our time, the number of inhabitants is still increasing with the greatest 
rapidity. 



TABLE-LANDS. 445 



CHA*PTER XVI. 

INFLUENCE OF THE RAISED OUTLINE OF THE EARTH ON MANKIND. — 
TABLE-LANDS, MOUNTAINS, HILLS, AND PLAINS. 

Throughout the globe tlie inequalities in level of the various conti- 
nents have a singular iafluence upon climate, and consequently, also, mod- 
ify in the most varied manner the destinies of nations. Instead of follow- 
ing one another regularly from .the equator to the poles according to the 
lines of latitude, the zones of temperature intersect and rise one above an- 
other; the surrounding conditions here and there are abruptly varied, and 
■with these conditions the populations also vary. 

Taking the mighty fabric of continents, there are some table-lands 
which are of the greatest importance in the history of mankind. Rising 
up in the midst of plains, with a system of mountains, rivers, and lakes pe- 
culiar to themselves, with a flora and fauna belonging exclusively to them, 
and a particular climate, always coldei*, and generally much drier, than 
that of the lower lands, table-lands offer the most diflicult barrier to the 
migration of nations ; for the wide seas, formerly quite impassable, are 
now easily crossed by ships, and nations of the same origin settle on op- 
posite shores, and become more and more united by voyages and com- 
merce. Table-lands in cold or even temperate regions are not merely 
boundaries between nations ; numbers of them are, indeed, nothing but 
deserts, on account of the dryness of the soil, the rigor of the weather, the 
violence of the winds, and the snow-storms. In South America, travelers 
can never venture without danger on the table-lands of the Andes, be- 
tween Chili and the Argentine Republic ; even in France, the almost un- 
inhabited causses of Levezon, Cavalerie, and Severac are very dangerous 
to cross in winter-time, and not unfrequently carriages are left there bur- 
ied in the snow. Most of the table-lauds of the torrid zone are equally 
desert, owing to the dryness of the air and the soil, and also on account 
of the thick saline beds with which the ground is covered ; but by a re- 
markable contrast, there are also certain table-lands which, in the region 
of intense heat, are the most favorably situated countries for the progress 
of man. Like rich, hanging gardens, rising to a height of 3000, 6000, or 
8000 feet in the air, these table-lands bear on their marble or granite pil- 
lars a fragment, as it were, of the temperate zone, with its climate, its 
products, and its comparatively prosperous people. Thus, the table-land 
of Ethiopia, peopled by a race distinguished from all others in Africa for 
its intellect, dignity, bravery, attainments, and progress, rises, like an enor- 
mous citadel, between the deserts of the west, the marshy valleys of the 
north and south, and the burning shores of the Red Sea. In the same 
way in America, the great Peruvian table-land once inhabited by the In- 



446 



LIFE. 



cas, the high lands of Granada, where the Muyscas and other Indian na- 
tions live, and the table-lands of Guatemala, Yucatan, and Anahuac are 
almost the only parts of the New Woi'ld where original civilization has 
spontaneously developed itself — flowers which could not grow in any 
other soil, yet brutally torn up by the conquering Spaniard. 

Thus it is according* to the latitude, the rain-fall, and the arrangement 
of the surrounding country, that table-lands have a favorable or unfavor- 
able efiect on the destinies of mankind ; on the one hand, as in the whole 
of Central Asia especially, there are thinly-scattered and often nomadic 
populations, in quest of springs and streams of water and fertile mead- 
ows, and very frequently also engaged in expeditions of murder and pil- 
lage; on the other hand, as in tropical America, there are comparatively 
peaceable nations, busied in agi'iculture, manufactures, and commerce, and 




Fig. 189.— Valgodemar. 

gradually developing their autochthonous civilization. Mountains also 
exercise very difierent influences' on the inhabitants of their valleys, ac- 
cording to the altitude of the lands inhabited, their temperature, and 
other climatic conditions, the nature of the rocks, the aspect of the slopes, 
and the abundance of light. How great, in this respect, is the contrast 
between the Italian valleys of the central Alps and the French valleys of 
the mountains of Dauphine ! The former are steeped in sunshine, bathed 
by the blue waters of the great lakes, and open widely on to the verdant 
plains of Lombardy ; from the summit of the headlands the villagers sur- 
vey an immense horizon, exhibiting, as if in a perfect picture, the most 
charming varieties both of land and cultivation. On the contrary, in 
the dreary district of Valgodemar, in the gloomy valleys of Devolny, the 
mountaineer sees nothing around him but crumbling rocks, barren steeps, 
and scanty crops of barley or potatoes produced, as it were unwillingly, 
by the stony soil. During part of the winter, the sun, which is hidden 



INFLUENCE OF MOUNTAINS. 



44V 



by the high mountains rising to the south of Valgodeinar, describes its 
daily course without the inhabitants of tlie valley seeing any thing but 
its pale reflection on the distant summits; and when it appears again in 
the happy days of spring, they gret^ it as a divinity. The village* of 
Andrieux, built as it is in a basin of the valley, remains for a hundred 
(lays hidden in the shade, in the midst of the pale white snow; therefore, 
who can express the joy which is felt when the imprisoned inhabitants, 
on the look-out for the first ray, see it dart like a luminous arrow above 
the crest of the forbidding mountains ! In the valleys of the Alps, the 
shivering inhabitants have built nearly all their farm-houses on those 
slopes of the pasture-lands which are the best lighted by the sun. (See 
Fig. 190.) 




Fig. 190.— Valley of the Plessur. 

Some no less striking contrasts among the inhabitants themselves cor- 
respond to the great diversities presented by the outline and trend of the 
mountains. The finest race of men are found living in the high valleys 
and on the sides of the Caucasus ; most of the inhabitants of the Alps are 
also remarkable for strength and health ; and yet, notwithstanding this 
fact, Switzerland is the country which, iVi proportion to its size as com- 
pared to the whole of Europe, has the largest number of cripples and 
other infirm persons. Cretins may there be counted by thousands, just 
as in Savoy, the Pyrenees, and nearly all mountainous countries. What- 
ever may be the special cause or the various circumstances which predis- 
pose to cretinism and to the infirmities caused by goitre, whether it be 
the want of aeration in the streams, the absence of iodine in the water 
which is drunk, or the rarity of the sun's appearance, still it is a fact that 
idiots and persons aftected with goitre are to be met with much oftener 
in gloomy mountain valleys than in open plains lighted by the sun, open 



448 LIFE. 

to all winds, and watered by broad rivers. Even lately, many a village 
of Savoy, such as Bozel or Villard-Goitreux, had more than a third of the 
number of its inhabitants composed of idiots with deformed necks. Ac- 
cording to Caldas, a tenth part of tfie population of JSTew Granada livino- 
in the narrow space between the wooded steeps of the high summits and 
the shores of the Magdalena and Cauca and their tributaries, are placed 
by the sad ^nalady of cretinisme outside the very pale of conscious hu- 
manity. Thus the most picturesque countries are sometimes inhabited 
by men in the most degraded state of existence. 

Notwithstanding all the varieties exhibited in mountain nations, it may 
be asserted in a general way that they are distinguished for courage and 
firmness. Their broad chest, containing lungs with more ample and nu- 
merous cellules than the lungs possessed by the inhabitant of plains, is 
filled with both a purer and a lighter air;* their eyes, well accustomed to 
look down fi'om some elevated cliff into the depth of the valleys, and to 
discern afar ofi" animals cowering in the hollows of the rocks, are bold, 
and glitter with a piercing lustre; their features are expressive, and their 
head -nobly set on their should'ers; with an even and quiet gait and a 
firm step,^they climb the steepest rocks, and bound over the glaciers in 
pursuit of the chamois. Their daily toil is most laborious, and nothing 
but a courage and perseverance proof against every trial, enables them to 
obtain the food necessary for their support. In many spots the ground 
is so steep that it is impossible to make use of animals in cultivating it ; 
there are some mountaineers who plough the furrows with their own 
hands, and lay dolvn manure to cover over the seed ; sometimes, even, 
they are obliged to carry on their shoulders the fertile mold brought 
down into the low grounds by torrents and avalanches. In winter they ' 
are besieged by snow, and blocked up in their houses, so that frequently 
they are unable to go from village to village without peril of their lives. 
It is not, therefore, surprising that at the first approach of cold weather 
they begin to think of leaving their homes and descending toward the 
plains, which they speak of admiringly as " level as floors." From every 
valley of the mountains of Auvergne, the Pyrenees, the Alps, the Aj)en- 
nines, the Caucasus, and the Atlas, troops of mountaineers come down 
each year. Some work for the agriculturists of the lower lands ; others 
follow some trade learned during the interminable leisure of past win- 
ters. Actuated \>^ love for their fai*-distant family, no business comes 
amiss to them ; they deny themselves every pleasure, and, greedily econ- 
omizing the smallest gains, constantly labor to increase them. No genius 
is so full of resource as theirs, and by a sort of tacit agreement they have, 
throughout all Europe, distributed work among themselves, mutually 
sharing in the various itinerant trades. Among them the peddlers each 
have their own peculiar line of business. There are some, like those of 
Venose, in Oisans, who visit the lai-ge towns, with rare plants from their 
pastures, or minerals from their rocks ; others sell tools, engravings, or 
* Alcide d'Orbigny, Journey in South America, vol. iv., p. 124. 



PATRIOTISM OF THE MOUNTAINEERS. 449 

coarse stuflfs ; and, lastly, there are some wlio, as thousands of Swiss re- 
cently were in the habit of doing before it was thought a scandal to their 
country, gave themselves up to the vile trade of becoming a soldier in 
the service of either enemy or friend. 

Nevertheless, although at the first approach of cold the mountaineers 
emigrate in troops, it is almost always with the intention of returning, 
like the swallows and storks. Villages which are nearly deserted during 
the snowy months are peopled again in the spring, and the petty trades- 
man of the plains sets himself courageously to the hard work of cultiva- 
ting the barren soil which covers the rocks. The high summits are too 
beautiful, and too vividly impressed on his mind, for him not to love them 
involuntarily, as it were, and when far away from them he is always long- 
ing to see them again. In level countries, which he admires so much on 
account of the evenness of the ground, he looks back with afiection to 
the sloping and rocky fields of his native land, the narrow meadows 
perched on the edge of precipices, the white snow heaped up on the beds 
of rock, and the bright summits, which in the morning reflect the first 
gleam of dawn, and in ^he evening are lit up by the last ray of the set- 
ting sun. The inhabitant of level plateaux meets, in his migrations, with 
a nature like that in which he has lived all his childhood, and delights in 
roaming over unlimited space, without even thinking of the steppes where 
he was born ; but the mountaineer can never forget his native valley, 
which is all in all to him ; and if he leaves it forever, he must be forced 
by the direst necessity. This love of country is the only reason why the 
people of the Caucasus, the Alps, and the Pyrenees, who are, notwith- 
standing, so brave when they have to defend their native land, have never 
made any permanent conquests in neighboring countries. After every 
victory they retire to their own narrow territories, separated from each 
other by transverse ridges of rock difiicult to cross, and while they are 
dispersing, their vanquished enemies in the plain reconstitute themselves 
into powerful combinations. The pre-eminently victorious nations are 
those which inhabit monotonous plateaux or boundless low-lands. The 
most extensive empire that ever existed was that of the Moguls. It ex- 
tended from the Vistula to the Yellow Sea, and from the Frozen to the 
Indian Ocean. Like swarms of locusts, the hordes became diminished in 
their course by battles and sickness, but none the less always kept march- 
ing straight on in their rage for massacring men and conquering territory. 
At the present time, is not Russia the great invading power, and does a 
single year pass without her adding either the territory of a tribe or some 
fragment of a kingdom to her own enormous empire, already extending 
over the seventh part of the whole continental area? 

Looking at the question in quite a general point of view, it may be said 
that the countries where the topographical outline afts most favorably 
on the nations which inhabit them are the gently undulating lands of the 
temperate zone, where valleys well watered by streams and rivers alter- 
nate with hills, where the landscapes are beautiful, though not with a wild 

29 



450 LIFE. 

beauty, and the communications are naturally easy. The largest part of 
France, Germany, England, and the United States present exactly these 
conditions, and that is one of the principal causes of the comparatively 
rapid progress made by the various peoples of these countries. More- 
over, even in these lands where the race is renewed every day by the in- 
termixture of families, where men and things are constantly mingling, and 
thoughts are speedily communicated from one place to another, it is easy 
to notice the contrast which is presented between the inhabitants of each 
region, according to the difference in the land and local climate. The 
people themselves never make a mistake, and are always able to mark out 
the frontier which separates two I'egions naturally divided. Thus, speak- 
ing only of France, the fact has often been recognized, that the outlines 
of the ancient Gallic pagi corresponded pretty exactly with the barriers 
of the geological formations, and in our time most of these pagi would 
again become reconstructed if an administrative centralization did not 
roughly oppose the action of natural affinities. Every soil brings forth 
its own special race ; granite, calcareous soils, and even the region of lavas 
and extinct craters; wide fertile valleys, and thejbelt of marshes and of 
sands, are all alike in this respect. The popular name given to each prov- 
ince applies both to the soil and to the man who inhabits it; it explains 
and sums up the whole of the local geogi-aphical facts, and depicts the 
population itself, with its physical features, its mannei's, habits, trade, and 
state of civilization. The natural harmony existing between the land 
and the people is so striking; that when we speak of Touraine, Poitou, 
Auvergne, La Marche and Limousin, Saintonge and Perigord, the Landes 
and Armagnac, we might almost fancy that we had before our eyes the 
aspect of these countries and the features of their inhabitants. 

This very variety, this contrast between different provinces, forms one 
of the most important elements in the strength and pi'osperity of a nation, 
provided that these oppositions are not too numerous, and that they do 
not produce a violent breaking up into fragments and mutual antagonism, 
but are of a character to blend into one superior unity. Granite, chalk, 
sandstone, gravel, barren clays, sloping hills, moorlands, and sands mingle 
their various influences on the populations which inhabit them, and cor- 
rect what may be too monotonous in the mind and manners of those who 
cultivate wide fertile plains. Agriculture may truly be said to be the 
mother of all civilization ; laborers become attached to the soil from 
which they derive their own and their children's food; they detest wars 
which devastate their fields like a storm, and bui-n down their cottages 
as if with fire from heaven. Partaking of the nature of the soil which 
they cultivate, they are stubborn, patient, and quiet ; from father to son, 
and century after century, they oppose violence and rage with a passive 
resistance which intimately tires out the most energetic wills and van- 
quishes the proudest conquerors ; they battle with the very elements 
themselves; and if a storm destroys their houses, or a flood sweeps them 
away, they will resign themselves to famine, and, depriving themselves of 



PEACEFUL INFLUENCE OF AGIilCULTURE. 45 1 

the corn on which they feed, will courageously sow it in the too deceitful 
furrow. These high qualities are among those which are the most neces- 
sary in the work of the formation of a nation ; but if the cultivators oi' 
the plains had not to undergo the various influences of the more restless 
populations of the hills, the table-lands, and sea-shores, further progress 
would ultimately become impossible for them.* As regular in their hab- 
its as the seasons in their annual course, rooted, so to speak, to the soil 
like the plants they cultivate, a mere routine would be their only law, 
their only ideal would be immobility, and their only hope in the future 
would be the maintenance of things as they were. 

* See below, p. 455. 



452 LIFE. 



CHAPTER XVII. 

INFLUE^rCE OF THE SEA AND ETJlSrNING WATERS. TRAVELING AND COM- 
MERCIAL NATIONS. ISLANDS AND ISLANDERS. 

The ebb and flow of the waves exercise a great power of attraction on 
nearly all men, and must certainly be considered as adding a large por- 
tion to the population of sea-shores. Savages especially, who always 
obey their first instinct, yield readily to the fascination which water exer- 
cises upon them. In the islands of the Southern Ocean, which are still 
peopled by barbarous tribes, the sea-shore is the only inhabited part, and 
the villages form round the mountains of the interior a ring as regular as 
that of the banks of coral. It must be confessed that the islanders seek 
their food in the sea and on its shores, and the coast affords them the 
greatest facilities for trade and communication. The numberless fish and 
mollusks, which frequent the sea in the vicinity of most of the coasts^orm 
an abundant source of food, which legions of fishermen may draw upon' 
without fear of exhausting it. The shore and the waters which wash it 
form the readiest means of communication for the inhabitants, and allow 
them to go and exchange their fish for other commodities. We have here 
the beginning of commerce, and the origin of the modern movement 
which spi'eads in all directions across both land and sea, laying hold of 
the riches scattered far and wide, and circulating them from one to an- 
other like, as it were, the life-blood of nations. 

These commercial facilities, which are enjoyed by the still barbarous 
people of many an island-coast, must exercise the same influence to a 
much greater extent over civilized nations, always anxious to be in rela- 
tion with one another by the interchange of news and commodities. Thus 
the small islands of the West Indies and the scattered isles in the Atlan- 
tic, as well as Mauritius and Reunion, in the Indian Ocean, are inhabited 
almost exclusively on their outer edge ; in many of these lands the inte- 
rior remained a long time almost unknown, although the colonists, coming 
for the most part from colder countries, would have found it to their ad- 
vantage to seek in the lofty valleys and on the mountain slepes a climate 
similar to that of their native land. In the same way, on the continent, 
considerable populations are massed in the vicinity of the coast, and not 
unfrequently a line drawn from any central plateau to the sea crosses re- 
gions increasing in population as it gets nearer the coast. In the interior 
of the country the people are in the habit of settling on the shores of 
lakes, which are, in fact, miniature oceans, or along the rivers and other 
water-courses, which the Chinese so rightly call " the children of the sea." 
Houses, gardens, and cultivated lands border continuously both banks of 
every large river in temperate Europe, and villages and towns are found- 



INFLUENCE OF THE SEA ON MANKIND. 453 

ed at every confluence where a tributary joins the j)rincjpal water-course ; 
thus, as is often said, the Seine, the Thames, the Rhine, the Rhone, and 
the Loire are nothing but long moving streets uniting one with anothei- 
the fragments of the immense town which borders their banks from the 
source to the mouth. The lakes of Constance, Ziirich, and Geneva are also 
surrounded by dwellings and gardens as though with a belt. Toward 
the eastern extremity of Lake Leman, from Vevey to Villeneuve, the cha- . 
teaux, hotels, and country-houses connect one village with another, so as 
to form one splendid city ; and certainly the beauty of the scenery, much 
more than the advantages of navigation, is the point which has made this 
lovely shore one of the most frequented and populous parts of Europe. 
The beautiful view of the verdant headlands, of the white shores, and the 
blue Mediterranean, is the cause why the coast of Liguria for more than 
thirty-seven miles in length, from Savona to Genoa, and from Genoa to 
Chiavari, has been covered with palaces and marble villas. 

Those who live immediately on the sea-shore, and from their dwellings 
can hear the nbise of the waves, have generally a natural instinct to set 
sail upon them. The unlimited horizon which is spread before them in- 
. spires them with the love of space, and the never-ending succession of 
waves is constantly inducing them to rove over them. It must be con- 
fessed that when the coast is totally destitute of ports, bordered by sand- 
banks and rocks, and exposed to all the force of the waves and storms, 
the sea-shore populations can not have that instinctive " soul of iron " 
which leads them to embark cheerfully on the surge in mere rafts or frail 
canoes ; foreign nations, who are more favored in the situation of their 
coasts and the tranquillity of their sea, are the guides from whom they 
must learn the art of building ships and guiding them over the waves. 
On the other hand, the inhabitants of coasts washed by waters which 
are nearly always still, and indented by harboj^ where vessels can take 
refuge during a storm, give way to the instinct which attracts them to 
the sea, and the taste for travels and adventures is gradually developed. 
When the Spanish discoverers sailed for the first time along the coasts of 
Central America, they were surprised to meet with trading canoes " al- 
most as large as their galleys," and capable of carrying about fifty per- 
sons. And more than this, off the Peruvian coast the traders in jewels 
and stuffs were in the habit of venturing on mere rafts, and, allowing 
themselves to be carried along by the current and driven by the breeze, 
traveled hundreds of miles along the coast.* 

Next to the exceptional advantages afforded to maritime populations 
by a large number of safe ports and a rarity of storms, the most favorable 
condition for the development of commerce and navigation among rising 
nations is the vicinity of an island or archipelago, the dim ou|Jine of 
which is seen over the blue expanse of the sea, and invites from afar as if 
by some secret magic. In the same way the timid fledgling flies out from 
its nest to reach tlie nearest branch. The islands of the ^gean Sea were 
♦ Prescott ; O.scar Peschel, Ausland, No. 7, 1868. 



454 LIFE. 

the mid-points w»bich attracted the mariners from Asia Minor toward 
Greece ; and Cyprus appeared to the Phoenicians as their first point of 
progress before they went out into the main sea. The island of Elba,. 
hardly visible from the coasts of Tuscany, forms, as it were, one stage on 
the way to Corsica, the Balearic Isles, and the distant shores of Spain ; in 
the same way the white cliffs of Great Britain, which sometimes appear 
above the Channel like a floating mirage, were a constant fascination, so 
to speak, to the inhabitants of the opposite shore ; and this is the reason 
why, after having been so often invaded and conquered, she has ultimate- 
ly become the principal commercial emporium of the whole world. Isl- 
ands, those " pearls of the sea," are the features to which the surface of 
the globe owes some of its most charming aspects ; and, thanks to com- 
merce, these islands are likewise the cause to which nations are indebted 
for a great part of their civilization. As Ritter loved to repeat, it is diffi- 
cult to imagine how the course of history would have been changed if the 
islands of Greece, Sicily, and Great Britain had never formed a part of 
Europe. If the Aryan nations had been deprived of citadels of this kind, 
in which they could, as it were, shut themselves up, and so keep safely 
the treasures won by their intellectual and moral conquests, they would 
certainly never have attained the progress which has made the modern 
world what it is. Steeped in ancient barbarism, they would have remain- 
ed strangers 'to one another; although the earth is so small, the whole of 
its circumference would never have become known, and mankind would 
still remain unconscious of its full power. 

Nevertheless, before the navigation of the main sea had connected one 
with another all the points on the surface of "the globe, islands could not 
fill any important place in the history of mankind, unless they were situ- 
ated in the immediate neighborhood of a continent, and depending, so to 
speak, on a land with ri^ plains and a numerous population. Islands, 
standing alone far out in the sea, are like prisons or places of exile to the 
tribes which inhabit them ; even the very facilities they offer for voyages, 
the stimulus of the wind as it passes, blowing toward other countries, the 
fascinations of the waves with the mirage moving on them, the indistinct 
shapes appearing beyond the horizon, calling to the mind's eye happy re- 
gions far away — all become a cause of inferiority as regards social devel- 
opment ; for when the islanders leave their little country to visit some 
distant land, they seldom return to their native soil. The want of a cen- 
tre of attraction round which the inhabitants can gravitate keeps them 
in a state of isolation and primitive barbarism. Just as in some of the 
lower organisms in which the head is wanting, life is spread generally over 
the whole body ; but it is not concentrated in any one part, and can not 
be vei"j( intense. Thus it is that those wonderful isles of Oceanica, so nu- 
mei-ous, so beautiful, and possessing such a fertile soil and delightful cli- 
mate, have remained beyond the pale of the civilization of the world : 
scarcely two centuries ago they were still almost entirely unknown. 

At the present time the regions best suited for the progress of mankind 



ISLA^WS AND IHLANBERS. 455 

are, therefore, the wide continental plains which look out over the sea to- 
ward neighboring islands and archipelagoes. These fertile regions, which 
also, in most cases, have formerly been gulfs now filled up with marine or 
fluviatile alluvium, attract a numerous population. These countries with 
level soils are the spots in which agriculture develops itself, and the ad- 
jacent ports are those to which commerce is directed, where commodities 
are exchanged, and where men learn to know men, and thouglit mingles 
with thought. Near^ all the mightiest cities are founded on the points 
where the sea-shore and agricultural regions come in contact; crowds 
gather tliere because all the great interests of humanity are there united. 
By a singular contrast, an agricultural population, which is the most sed- 
entary, and, by its mode of life, no less regular than the return of the sea- 
sons, and disposed to be the greatest slave to routine, is often found in 
immediate contact with the maritime class, the most unsettled, the quick- 
est in action, and the fondest of travels and adventures. This juxtaposi- 
tion of men so diflerent in mannei's is one of the most imjDortant facts in 
the history of human progress. 

There are maritime nations whose life is one continuous voyage, having 
made, as it were, the ocean their, home. Thus the Normans, who called 
themselves the " kings of the sea," were in the habit of sailing from shore 
to shore, carrying with them terror and destruction, and conquering na- 
tions as they passed along ; then re-embarking in their light vessels, and 
crossing the vast tract of sea, they discovered the continent of America, 
which, after their time, remained five hundred years wholly unknown. 
A similar case is presented by the pirates of the Sunda Archipelago, 
whose countless boats infest the waters of the Pacific, and who, although 
massacred in numbers, never cease to multiply, as if they sprang from the 
waves. And where do those who are born on the shores of England pass 
the greater part of their lives ? On the deck, under the mast, amidst the 
rigging and the waves, scannmg the clouds and the blue sky. Maritime 
peoples ai-e always intrepid; they engage in too many terrible conflicts 
with storms, gusts of wind, and death under its thousand aspects, for them 
ever to tremble before their fellow-men ; they ai-e endowed with coolness 
and perseverance, for their struggle against the elements must often be a 
severe one ; and, in order •to conquer nature in all its fury, they require 
the courage of reflection more than that of enthusiasm. Their ideas are 
calm and energetic, but commonplace, like the sea they sail upon ; they 
rarely suggest to them either grace or gentleness, but strength and some- 
times violence. As a child of the ocean, the sailor presents in his life some- 
thing like a reflection of the mighty billows on which he has been cradled 
since his infancy. 



456 LIFE. 



CHAPTER XVIII. 

BLENDING OF DIFFERENT CLIMATES. — THE INFLUENCE OF CIVILIZATION ON 
' THE FEATUEES OF A COUNTRY. 

Such, then, in an entirely general point of view, *e the influences of va- 
rious climates on the populations which inhabit them ; such, too, are the 
ethnological contrasts produced by difiference in zones, continental relief, 
aspect, and the nature of the soil. Nevertheless, these contrasts rarely 
present themselves in a distinct and- decided manner ; it is impossible to 
trace out the boundaries between nations with a ruler and compass. The 
influence of winds and currents, the presence of inland seas, the gulfs and 
promontories of continents, the curves of the mountain chains, and the 
countless physical features of the earth, have a constant tendency to alter 
and intermingle the climates. In many cases even contrary forces tend 
to balance one another, and, consequently, the contrasts are weakened and 
die out. Thus the ground is low in almost all the cold northern coun- 
tries, and during the warm season it receives the whole salutary action 
of the tun ; the inhabitants of northern regions, therefore, resemble the 
mountaineers on account of the severity of the climate which surrounds 
them, and the people of the plains on account of their low country. Fai- 
ther south, the mountaineer of the temperate or even the torrid zone may 
call himself a northerner because he lives in the midst of snow, or a south- 
erner because the rays of the sun descend to him from the zenith, and dis- 
tricts of exuberant richness lie spread before him at his feet. In the same 
way, if the peak on which he dwells rises from the midst of the sea, he 
may also be called a child of the ocean, and his character will certainly 
exhibit some striking contrasts to that of the inhabitant of a mountain 
situated far in the interior of a continent. The endless varieties in water, 
air, and situation, and the more or less rapid vibration of luminous and 
magnetic waves, are constantly modifying the general aspect of nature. 
Every province, city, and hamlet has its own 'peculiar climate, and this 
climate again has nothing permanent about it, and varies every moment. 
All climatic facts demonstrated by observation blend into one another, 
and consequently it is impossible to judge of their action on nations ex- 
cept from an entirely general point of view. 

And this is not all ; nations do not rest forever on the soil where Jfchey 
were born, but between them and their neighbors there is always taking- 
place a more or less active interchange of isolated individuals and of fam- 
ilies ; sometimes, indeed, nations are forcibly united by conquerors, who 
transplant whole peoples, or else the vanquished go and seek a new coun- 
try beyond the seas or mountains in a totally different climate. In this 
case the climatic forces come into action, and modify the primitive type 



CHANGES CAUSED BY CIVILIZATION. 457 

of the man fcliiis removed from his native soil, and Substitute for him a 
new type in conformity with the nature which surrounds him. This strug- 
gle between the past and present, between men and climate, and not the 
account of the battles of armies and the crimes of kings, are the facts which 
constitute real history — that is to say, the evolution of man in his connec- 
tion with the globe. 

Moreover, even if nations do not change their country nor intermingle 
with other nations, their wants and habits become modified with the vari- 
ous changes in the state of society, and consequently the influence of the 
nature which ^surrounds them varies century by century. Thus great for- 
ests, where the number of inhabitants depends totally on the quantity of 
game, are no longer suitable to man when he becomes an agriculturist ; 
trees fall under the axe, and the continually widening clearings are filled 
with corn-fields ; the climate' changes, and reacts on the populations who 
crowd into the cleared areas. The reclamation for cultivation of steppes, 
low and marshy lands, and all formerly desert regions, also results in mod- 
ifying the surroundings and the people who live there. The great naviga- 
ble rivers, with their whole net-work of streams and canals, are scarcely 
made use of by uncivilized tribes, and, only to adduce one instance, the 
immense river of the Amazons, the most magnificent track for commerce 
possessed by the interior of any continent, has scarcely, during past cen- 
turies, exercised any appreciable influence on fhe development of civiliza- 
tion among the populations on its banks.* By means of trade, rivers, on 
the contrary, become to civilized nations the principal material agents of 
progress*, until the creation of more rapid and artificial ways of commu- 
nication have lately diminished the comparative importance of the roads 
afibrded by nature. We find villages grouped along the great highway 
even when the latter do not run through the middle of the valleys, but 
traverse plateaux exposed to the wind, and destitute of the water neces- 
sary for use ; occasionally, indeed, the whole road seems converted into 
one long street, every peasant desiring to live on the line along which 
foreign traders. pass. Railways, also, have their part in the movement of 
population, and each station becomes an attractive centre round which all 
the inhabitants crowd. Beds of metallic ores, deposits of coal, marble, 
gypsum, salt, and other riches contained in the earth, are also, according 
to the state of civilization, treasures either unknown or neglected, and are 
elements either useless or of the highest importance in history. Califor- 
nia a district almost unknown five-and-twenty years ago, has, owing to its 
gold mines, become one of the greatest centres of activity on the surface 
of the globe. 

Even the •l-aised outline and the general disposition of countries may 
be, in turn, either useful or disadvantageous, according to the various 
jepochs in the life of nations. Thus the barbarous peoples which preceded 
us on the soil of Gaul and the other countries of Europe, took refuge in 
caves among the rocks, or built their huts on piles driven into the bed of 
* Oscar Peschel, Ausland, 1868. 



458 



LIFE. 



some lake. Subsequently, when a continual war of ambuscades and mas- 
sacres between neighboring tribes had given place to a somewhat less 
troubled state of society, the troglodytes came down one after another 
from their gloomy caves ; the lake-dwellers left their unhealthy roosting- 
places and settled on terra firma, under the shade of the wide-spreading 
trees ; the water of the lakes, which formerly protected them from all at- 
tacks, had now become a danger to them by separating them from the 
land, where they found the means of existence. During the terrible iron 
ages of feudal life, the great lords erected their castles like vultures' nests 
on the summits of impregnable rocks, grouping the humble cabins of the 
peasants at the foot of their lofty ramparts ; the towns themselves, no less 
than the castles, were confined to the crest of some declivity very difficult 
of access. At that time, the primordial care being that of defense, each 
group of habitations was placed at the. summit of some lonely peak, sur- 
rounded by walls and bristling with towers. In the south of France, in 
Spain, on the coasts of Liguria, in Tuscany and Sicily, nearly all the old 
villages are perched up on the heights, and, looked at from below, their 
crumbling walls resemble fantastic escarpments of the rock; the houses, 
built up on the outer rampart, have no windows but the narrow defensive 
loop-holes ; the corner buildings are battlemented and machicolated tow- 
ers, furnished with portcullises ; the church, built on the highest point, 
forms also the citadel of !he villasfe. But in modern times the first re- 



niM w^ 



l^^^^^^Mff^^f^ll^^^^ 




Pig. 191.— Villages of Aliermont. 



ANCIENT FORTIFIED TOWNS. 



459 



quirement is-that of labor ; tlie inhabitants, therefore, aoandon one after 
the other their eagle-like eyries, and go and settle on the sea-shore, the 
banks of some river, or the edge of the roads which pass through the 
plain. Like those sea-animals which get rid of a shell that has become 
too small for them, they emerge from their picturesque turrets and build 
themselves dwellings, less beautiful, perhaps, as a detail in the landscape, 
but much more healthy and comfortable. 

Even in the least civilized countries of Europe the towns have been 
transposed from their lofty summits, and have been established near the 
sea-coast. On the northern coast of Sicily, every marina increases at the 
expense of the borgo, and the old town ultimately becomes a splendid 
ruin, rising, like a mass of rocks, on the crest of the lofty mountains. 
There are still, however, towns containing several thousands of inhabit- 
ants situated on mountain ridges far above any cultivated lands; thus, 
in Sicily we have Monte San-Giuliano and Centorbi. The former, built 
on Mount Eryx, formerly sacred to Venus, occupies a narrow plateau 
2300 feet above the sea and the plains of Trapani. The town of Centorbi 
commands the plain at a height of more than 3280 feet. The inhabitants 
who cultivate the fields lying at the foot of the mountain are obliged 
every day to go up and down an endless flight of steps winding in 
among the rocks and hemmed in by precipices. In front, on the other 
side of the valley of the Simeto, and at the edge of a stream of lava 
which has run down from Mount Etna, stand the mansions of Aderno. 
The clouds which float across from town to town traverse this space in 




Fig. 192.— Monte San-Giuliano. 



460 LIFE. 

a few minutes; standing on the edge of the cliff of Centorbi, one may 
even inhale the perfumes of the gardens on the opposite terrace ; but to 
accomplish the distance separating the two localities, the time needed is 
as great, or greater, than that required to travel from Paris to the Belgian 
frontiers, or to the coasts of the Channel. It is evident that a state of 
things like this must shortly be altered. The citizens, who shut them- 
selves up everyday within their ancient walled inclosures, need not now 
feel any dread in establishing themselves in the midst of tracts of land at 
present uninhabited. The steepness of the escarpments and the difficulty 
of access, which were formerly esteemed by them as a privilege when 
their life was one continual terror, ought henceforth to appear, that which 
they are in reality, a most disadvantageous loss of time, and a deplorable 
cause for an inferiority in civilization. The summits of lofty mountains 
will no longer be favorite sites for the building of towns, until man has 
become a lord of the air by being able to steer balloons, and until the 
most favorable landing-places for him are peaks and ridges. 

These successive changes in the more or less considerable adaptation 
of the earth to the nations inhabiting it, take place no less in respect to 
the outline of the continents themselves than in the trifling details of lo- 
cal topography. Thus the numerous bays which run into the coast of 
Europe, and the peninsulas which project in every direction, and contrib- 
ute so largely in giving to the people of this pai't of the world the first 
character in history, are constantly losing in comparative importance, in 
proportion as the inland ways of rapid communication increase; it may 
even be asserted that, in all countries now intersected by railways, the 
indentations of the coast, once so useful, owing to the natural water-ways 
they presented for navigation, have become an obstacle rather than an 
advantage. Thus, until lately, great commercial ports were necessarily 
fixed at the land-side of the hollow formed by the shores of a gulf, or 
else on the banks of the estuaries which run the deepest into the conti- 
nent; for this position enabled them to receive, by the shortest possible 
road, the largest possible quantity of commodities and merchandise from 
neighboring countries. In our time, owing to the i-apid means of com- 
munication, this is no longer the case, and maritime commerce tends more 
and more to take for its starting-place ports situated at the extremity of 
a peninsula. Every historical progress, therefore, changes the relation of 
man to the earth which he treads, and, consequently, the influence of his 
surroundings is incessantly being modified. 



THE COURSE OF HISTORY. 4^51 



CHAPTER XIX. 

THE COURSE OF HISTORY, — HARMONY EXISTING BETWEEN COUNTRIES AND 
THE NATIONS INHABITING THEM. 

It is the duty of historians to relate the course of nations across con- 
tinents and islands, and to point out the incessant action exercised upon 
them by soil and climate. Every mountain, every headland, every islet, 
every lake, river, or rivulet plays its part in the history of mankind. 
Nevertheless, the earth itself, and the events which have taken place 
upon it, are too little known for it to be possible yet to attempt a de- 
tailed description of the harmony existing between the human race and 
the globe during past centuries ; it is only possible to point out the chief 
features of the part which the principal regions of the globe have taken 
in the development of nations. 

The vast and compactly formed continent of Africa has not afforded its 
inhabitants the opportunity of forming relations with other populations 
of the globe ; in the north only, the Berber tribes, occupying the slope of 
the Atlas facing the Mediterranean, and separated from the rest of Africa 
by the great desert, have been associated in a slight degree with the 
movements of European civilizations. With regard to Egypt, whose in- 
fluence has been so great over Greece and the Eastern world, it must be 
considered as forming a little world by itself, to which the remainder of 
the continent was as an unknown land. In the vast inaccessible area of 
equatorial Africa, men were born, and died, generation after generation, 
without knowing that other men like themselves lived beyond the bound 
aries of their country ; in their view, the entire universe was comp^-ised 
within the limits of their horizon. Favored by constant heat and fertile 
lands, they had not sufficient ambition, and did not tax their ingenuity 
to render their life more easy. Left to their own resources, they lived as 
their ^^ncestors had lived : during the course of centuries, therefore, civili- 
zation could make but imperceptible progress among them. Almost up 
to the present time, as is well known, most of the inhabitants of Africa, 
belonging to totally different races — Caffres, Hottentots, Congos, Mozam- 
biques, Ashantees, Penis, and Yolofs — have remained in a state bordering 
on primitive barbarism. 

The numerous archipelagoes scattered over the Pacific Ocean must, on 
account of their dispersion, have been as unfavorable to the rapid prog- 
ress of their inhabitants as was the enormous pile of Africa, on the 
other side of the world. Previous to the discoveries of modern naviga- 
tors, every island in the Southern Ocean was a small separate world, 
where, owing to the fertility of the soil and the beauty of the scenery, a 
rudimentary society was developed ; moreover, the facility afforded for 



462 - LIFE. 

navigation in these seas, which are generally smooth, and swept by (Tegu- 
lar winds, enabled the migration of tribes to take place to a very consid- 
erable extent. But no sooner were these new connections formed, than 
the old ones were broken off; the savages who had repaired to their fresh 
country were forever separated from the former one. In consequence of 
the fatal isolation of the various groups of people, no great mutual inter- 
est and no idea in common can link together all the tribes of the Pacific. 
This portion of mankind, imprisoned, as it were, in the different islands, 
has remained broken into fragments, never destined to be reunited. 

In the east of Asia, the inhabitants of the coast of China and the isl- 
ands of Japan were more fortunate than the islanders of the Southern 
Sea. In these countries of the Old World, the fathers could at least be- 
queath to their children their industrial skill and their acquirements; 
tribes could unite with tribes, and nation could instruct nation. The 
"central flower of the earth," that region vast enough to maintain hun- 
dreds of millions of inhabitants, is also in possession of numerous privi- 
leges; it sloj)es gently toward the sea, it is watered by wide navigable 
rivers, its sea-coast is indented by bays and promontories, and its temper- 
ate climate incites to labor by a regular alternation of seasons and crops. 
The insular part of this region is composed of an archipelago of several 
thousands of isles, and islets are grouped round the larger tracts of land ; 
the communication between these islands and the continent itself is al- 
ways easy. Thu^ the peoples of China and Japan have, by their own 
inherent energy, attained to a very advanced state of culture, and for a 
long series of centuries they were probably the foremost among mankind 
in respect to agriculture, commerce, trade, and practical philosophy. This 
civilization in the extreme east had, however, no outlets except toward 
the almost solitary tracts of the Pacific Ocean. On this side, the access 
to other continents and other nations was closed to the influence of the 
yellow race, and savants have cogent reasons for doubting the fact that, 
during the course of historic ages, any Chinese emissaries ever crossed 
the Southern Ocean and carried into the land of Fu-sang, now called 
Mexico and Guatemala, their religion, manners, and architecture. 

The tracts of land which extend obliquely across the Old World from 
Ceylon and the banks of the Ganges to the British Archipelago, owe to 
the favorable form of their outline and the harmonious distribution of 
their mountains advantages as great as, but different from, those of China 
and Japan. Descending from the plateau of Pamir and the circumjacent 
districts toward Hindoostan, Bactriana, and Asia Minor, the Arj^an race 
did not become divided into completely isolated nations. In spite of the 
lofty mountain chains of Soliman-Dagh and Hindoo-Koosh, in spite of the 
salt plateaux of Persia, and the cross ridges of Elbury, Ararat, and Tau- 
rus, the communications between adjacent countries were never interrupt- 
ed, and the industrial and moral attainments of the people did not remain 
absolute secrets to their neighbors. While each peculiar mode of civiliza- 
tion was worked out in its own special domain, it profited from those 



The Ocean, &c'. 



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Ei'Tlard. 



EARLY CIVILIZATION OF THE EAST. 463 

which were springing up afar off on other plateaux or on other plains ; 
the myths and the songs of India, bequeathed by the ancient Aryans, 
were known to the Persians, and the thoughts of Persia flowed back to 
the Hindoos; lastly, the religion and philosophy of both one and the oth- 
er, modified in their passage through time and space, were mingled and 
blended with the civilization of the Semitic nations, the Chaldeans, the 
Phoenicians, the Jews, and the Carthaginians. 

On the shores of the Mediterranean, the two countries of Egypt and 
Asia Minor, which bound the eastern part of this great sea, are the prin- 
cipal representatives of the first era in "Western civilization. In these 
two countries the state of society exhibited the most opposite contrasts, in 
consequence of the variety of races, manners, and climate ; but wars, com- 
merce, travels, extensive migrations, and lastly, science, were constantly 
tending to connect the two poles in the world's civilization. The union 
of the two contrary elements commenced in the beautiful country of 
Gi-eece, and then advanced farther on to Crete and the Cyclades, as if to 
serve as a rendezvous for the ships of Egypt, Phoenicia, Cyprus, Ephesus, 
and Troas. The ideal of all that the ancient communities had dreamed 
of as the great and the beautiful was realized in the little peninsula of 
Hellas, an harmonious combination of mountains, deep valleys, and penin- 
sulas scarcely noticeable on our maps, and yet the part of the earth where, 
up to our time, the glory of man shone forth in its greatest splendor. 
Nowhere else on the face of the globe does the earth assume forms so har- 
monious, and, so to speak, so living. The mountains, although of no great 
height, exhibit an outline of such great beauty, that they still retain their 
celebrity by the side of the giants of the Alps, Andes, and Himalayas ; 
and the names of Monte Rosa, Antisana, and Gaurisankar will never, per- 
haps, shine out with the same glory as those of Pindar, Citheron, Parnas- 
sus, and Olympus, the abode of the gods. On a diminutive scale, the small 
country of Greece exhibits, as it were, a summary of all continental fea- 
tures ; it has its plateaux, its piles of rock, its mountain ranges, its valleys 
and plains, visible and invisible water-courses, lakes, and gulfs ; the an- 
cients, indeed, went so far as to find there both heaven and hell. Its 
shores are curved into so many gulfs and bays, that the terminal peninsu- 
la resembles a dentated leaf floating on the waters. Every city had its 
river, an amphitheatre of hills or mountains, fertile fields, and an outlet 
toward the sea; every element necessary for the free association of men 
was there combined, and the neighborhood of rival cities, equally favored, 
kept up a constant spirit of emulation. Thus there never has been seen 
in the world any groups of republics so proud, and so favorable for indi- 
vidual scope of ambition. The little town, rendered illustrious by ^s- 
chylus, Sophocles, Phidias, Demosthenes, Plato, and many other men of 
genius, is still, after a lapse of more than two thousand years, the bright 
centre of historj^ 

At the time when the Hellenic republics were at the zenith of their glo- 
ry, local civilizations sprung up in Italy, Sicily, Iberia, and Gaul. In con- 
sequence of the geographical position of these countries, all the intellect- 



464 LIFE. 

ual and moral conquests of Greece and the East turned to their profit. 
By small degrees, and century after century, an h-resistible march of ideas 
continued its course from thg plains of Hindoostan to those of Western 
Europe. The revolutions in the history of modern nations are well 
known ; we know also how, after having succeeded in passing through, 
without extinction, the long and gloomy night of the Middle Ages, man- 
kind was " born again," owing to a twofold discovery which gave the so 
cieties of modern times a definitive scope of action. While poets, schol- 
ars and men of science were recognizing in the treasures of antiquity the 
free thought of Greece and the incisive genius of Rome, Columbus and 
other navigators were discovering the two continents of America, and 
thus completing the equilibrium of the globe. From that time the gradual 
civilization of all nations was assured, both by science and justice, in spite 
of violence of all kinds, wars, and hideous ignorance. The progress of 
each nation became that of mankind itself; all the islands and all the 
continents, once separated from one another, were united across the ocean, 
and became the common domain of man. At the very time when, owing 
to the discoveries of Copernicus, Kepler, and others, the earth, which was 
supposed to be limitless, was found out to be nothing more than an isola- 
ted globe revolving in sjaace, and no longer the centre of the universe, 
the inhabitants of this inconsiderable planet began to feel the conscious- 
ness of their own greatness, and out of this mass of nations and tribes one 
common humanity began to assert itself 

In consequence of that movement of civilization which, in the Old 
World, spread from east to west, following the course of the sun, the ports 
of Western Europe — Cadiz, Lisbon, Bordeaux, Nantes, Saint-Malo, Lon- 
don, Bristol, and Liverpool — are like so many conductors from which the 
electric fluid flashes forth, to cross the seas to the American continent. 
But there the movement must necessarily change its direction. The New 
World is not, like all great historic countries, placed in a parallel line 
with the equator; but, on the contrary, it extends from north to south in 
the direction of the meridian, and, thanks to this transversal position, Eu- 
ropean emigrants have been enabled rapidly to colonize the lands recent- 
ly discovered. Italian, Spanish, Portuguese, French, English, and Dutch 
navigators all found, both to the north and south of the equatorial line., re- 
gions with a climate similar to that of their native land, and in both zones 
they were able to found a " New Spain," a " New France," and a " New 
England." Added to this, both winds and currents cross the Atlantic 
obliquely, and bear the mariner toward those wondrous regions of the 
Antilles and Colombia, where nature, nothwithstanding the heat of the 
climate, exercises so great a fascination over European strangers. 

Emigrants from the Old World have thus established themselves all 
along the coast of the new continent for a length of more than 6000 miles, 
from the estuary of St. Lawrence to that of La Plata. At the same 
time, the breaks in the chains of the Cordilleras, in the isthmus of Central 
Amei'ica, enabled emigrants to colonize the western shores; also those 
which face toward China, Japan, and Australia. Thus, invading the whole 



COLONIZATION OF THE AMERICAS. 465 

length of both continents, the new-comers liave been able to go on and 
conquer the interior of America ; they have made themselves acquainted 
with its vertical outline, with its soils and with its products ; and these 
are now better known than the features of a great part of the»01d World, 
and they have founded in these but lately unexplored regions societies 
allied to those of Western Europe. The children of the emigrants have 
become nations, the power of which has prodigiously augmented when 
compared to the progress of the mother-country. In these virgin coun- 
tries, population, manufactures, commerce, public riches, all increase with 
unheard-of rapidity ; and it is an important fact in the opinion of some, that 
the United States of America, to some extent disentangled from the op- 
pressive institutions of ancient Europe, govern themselves by free democ- 
racies. The " Utopias " of the Ola World have become realities in the 
New World. America is the laboratory where the European ideal is 
brought into practical action for the jjublic good. 

The two Americas present a harmonious counterpoise as regards their 
continental masses, and, in a social point of view, exhibit a contrast which 
may be compared to that of their shapes. The northern portion, situated 
between Europe and China, is admirably organized to serve as a great 
thoroughfare for nations and merchandise traveling from the far east to 
the extreme west. Through it now passes the Pacific Railway, which 
continues on terra firma the line of stealhboats which on one side run be- 
tween New York and Liverpool, and on the other between Shanghai and 
San Francisco. In the interior of the northern continent, the inland sys- 
tem of great lakes and the gently undulating plains of the Mississippi af- 
ford to commerce and colonization facilities unequaled in any other part 
of the world. Nevertheless, the population which forms the United States 
is almost entirely composed of emigrants of European descent, and, un- 
fortunately, it has not as yet been able to blend either with the aborig- 
ines or with the race of slaves imported from Africa. 

South America is a continent of a more maritime character, and its 
ports, opening on the great southern seas, serve as intermediate landing- 
places in voyages of circumnavigation. In the interior, trade and coloni- 
zation find a province less favorable than that of the northern continent; 
the mountains there are loftier, the plateaux rise more steeply, the forests 
are more difiicult to cross, the deserts are more inhospitable, and the cli- 
mate is more to be dreaded by emigrants from distant Europe. Thus the 
South Americans have sufiered more than their northern rivals from the 
influence of their surroundings. Withoi* relinquishing their brotherhood 
with the nations of the Old World, they have gradually become mingled 
with the natives, and this fusion of races has been the means of introdu- 
cing those who were once savages into the sphere of modern civilization. 

North America may be more European, more characteristic, and more 
active in its character, but South America addresses itself more to the 
whole human race: to her belongs the honor of having invited many a 
still barbarous tribe into the great unity of nations. * 

30 



466 LIFK 



BOOK IV.— THE WORK OF MAN. 



CHAPTER XX. 

KEACTIOIf OF MAN ON NATURE. — EXPLORATION OF THE GLOBE. — VOYAGES 
OP DISCOVERY. ASCENTS OF MOUNTAINS. 

While society was in its infancy, Aen, either alone or grouped in small 
tribes, had to fight against obstacles too numerous for them ever to dream 
of appropriating the surface of the earth as their own personal domain ; 
they lived on it, certainly, but they timidly concealed themselves in its 
recesses like the wild beasts of the forest, and their very life was a con- 
stant struggle ; being continually threatened either with famine or mas- 
sacre, they were unable to devote any attention to the exploration of the 
country in which they lived, and those laws which would have enabled 
them to utilize the forces of nature were still unknown to them. Still, in 
proportion as nations became #eveloped in intellect and liberty, they 
learned to exercise a counteracting agency on that outer world, to the in- 
fluence of which they had passively submitted ; they gradually appropri- 
ated to themselves the soil on which they trod, and having become by 
dint of association actual geological workers, they altered in various ways 
the surface of continents, changed the system of running waters, modified 
the very climates themselves, and shifted the habitat of the different fau- 
nas and floras. Among the works which animals of a lower order have 
accomplished on the earth, the islets built up by the coral animal may, it 
is true, be compared with the works of man as regards their extent^ but 
these constructions are uniformly continued century after century, and 
never add a new feature to the general physiognomy of the globe. We 
always find similar kinds of reefs and similar tracts of land emerging from. 
the ocean like beds of fluviatile or marine alluvium ; while the works of 
man are incessantly being modified and give the greatest diversity of as- 
pect, to the earth's surface, renovating it, so to speak, with every fresh ad- 
vance of his race in knowledge and experience. 

The principal of all the conditions which will some day enable man to 
completely transform the surface of the globe, is that he must become 
fully and entirely acquainted with it and traverse it in every direction. 
Formerly, the savage or barbarous tribes, living entirely separate from 
one another, formed nothing but chimerical ideas as to the territories ly- 
ing beyond the narrow boundaries of their own country; they fancied 
they saw there nothing but an empty and limitless space, a gloomy and 
formidable world p^pled by monsters, but where man himself could not 



Tli(^ Oceiiii.&c 







lii.^hr f.rhavd 



HARPER, 



PL.XXllI 



^^olJ^il-_iourH,^^ 




Vl'V F,tha.rfl 



^V YOH.K 



EXPLORATION OF THE GLOBE. 467 

live. All the most remarkable features on the surface of the globe re- 
mained utterly unknown to them ; the inhabitants of the plains imagined 
the whole earth to be one great level tract of land, while those of mount- 
ainous regions pictured it to themselves as a succession of narrow gorges, 
cliffs, and summits. In the same way it appears that the Zunis, who lived 
far from the sea-coast, in the deserts now called New Mexico, were igno- 
rant of the very existence of the ocean ; on the other hand, numbers of 
the islanders of the South Sea were totally unaware that vast continental 
masses, extending over an area of many thousands of miles, divided the 
seas into separate basins. According to the testimony of Franklin, the 
Esquimaux learned with astonishment that toward the south lands exist- 
ed perfectly free from ice, and under the equator the ignorant inhabitants 
of the banks of the Amazon innocently imagine that their enormous river 
flows all around the world. 

In proportion as, by means of trade, travel, and even warlike expedi- 
tions, nations came to know the territories belonging to one another, they 
banished the idea of monsters into the mysterious spaces extending be- 
yond the boundaries of the explored world ; the sphere of knowledge in- 
creased simultaneously with the regions traversed, and the fanciful beings, 
such as gnomes or giants, who were supposed to retreat either toward the 
north or the south, bore away with them many of these superstitious and 
erroneous ideas. Thus the Greeks, who are represented to us by their 
mythology as contending in the earliest ages against centaurs and drag- 
ons, in the time of Aristotle and Plato fought only with men like them- 
selves ; and they localized the fantastic figments of their childish imagi- 
nation at points many hundreds of days' journey away on the other side 
of the Ganges and the columns of Hercules, in the burning deserts of 
Libya, or near the Hyperborean Mountains. Thus, in the Middle Ages, 
and even down to modern times, our maps of the world, like those of the 
Chinese and the*Japanese, represented all unknowij lands as inhabited by 
monsters ; but every new discovery made by travelers contracted the 
domain of flible, and quite recently the last mythical beings of geography, 
the tailed Niam-Niams, have finally been made to disappear 'from the cen- 
tre of Africa. 

Since the time when man first went round the world — that is to say, 
three centuries and a half ago — explorers have no longer had to venture 
into any region completely unknown : all they had to do was to connect 
with one another the lines of travel already traced out on the surface of 
the globe. This net-work of innumerable intersecting lines covers nearly 
the whole of the great continental masses, and extends over all that por- 
tion of the sea comprehended between the two polar circles ;«only toward 
the north pole, and on the opposite side of the earth in the antarctic re- 
gions, there still exist areas extending over a space of 2,900,000 and 
f^, 700,000 square miles respectively, which icebergs and mountains of ice 
have, up to the present time, kept intact from any exploration.* Those 
* Mittheibingen von Petermann, 1868. 



468 LIFE. 

spaces which still have to be exploi'ed at the two poles form nearly one- 
seventeenth part of the surface of the earth — that is to say, a tract equal 
to about sixty times the area of France ; in those regions there is still a 
very considerable extent of unexplored land and sea, and even in our days 
a few pusillanimous geographers have expressed a fear that these districts 
will remain forever unknown. Captain Cook, the brave navigator of the 
frozen j^ntarctic Ocean, asserted that no one had, or even could, approach 
any nearer to the pole than he had done. Pigafetta, also, in his account 
of the great voyage which he took with Magellan, givdfe as his opinion, 
" that in the future no sailor Would be bold enough to brave the dangers 
and fatigues of another circumnavigation of the world." It must certain- 
ly be confessed that fifty-six years elapsed before another sailor, Drake, 
brought to a happy termination a second voyage round the world ; in the 
present time nothing is thought of such voyages, so often are they accom- 
plished.* 

The energy with which the explorers of the polar regions have under- 
taken and are always ready to recommence their perilous voyages across 
the ice, is a sure guarantee of their future success; for though the obsta- 
cles remain the same, the experience of sailors and the resources of science 
are ever increasing. The discoveries which have still to be made in the 
centres of the vast continents 6f Asia, Africa, South America, and Austra- 
lia can not fail to be accomplished before very long ; for most of the dif- 
ficulties which impede travelers are of the moral order, and will gradually 
disappear, thanks to the progress of commerce and civilization. The hor- 
rible trade which makes the white man so justly abhorred in the centre 
of Africa, as well as in the basin of the Amazon, will soon come to an end ; 
the tribes, once appeased, will welcome the explorers, and supply them 
with guides ; groups of colonists, advancing by stages across continents, 
will form links of connection between the districts inhabited by civilized 
races. Every year the; spaces of land we still have to examine and trace 
upon our maps are diminishing in size, and hundreds of heroes, numbers 
of whom are destined to die in obscurity, are still further endeavoring to 
narrow them.* The most extensive surface which up to the present time 
has remained untrodden by the feet of European explorers, is that part 
of the African continent which is comprised between the sources of the 
Nile, the Congo, the Ogobai, and the Benue. 

. When man at last becomes acquainted with the whole surface of the 
globe of which he styles himself the master, when Columbus's saying is 
realized, "^^ mwn^o espoco'''' (the world is small !), the great geograph- 
ical work will then be, not to explore distant lands, but to thoroughly 
study every Retail of the country which we inhabit, to make ourselves ac- 
quainted with every river and every mountain, and to point out the part 
taken by each portion of the terrestrial organism in the life of the whole. 
This work, at the present time, is the task to which most of our savants, 
geographers, geologists,' and meteorologists are specially devoting them- 
* Oscar Peschel, Geschichte der Erkunde. 



ASCENTS OF MOUNTAINS. • 469 

selves, and important societies are being formed in every direction in or- 
der to push on local explorations. These societies address themselves 
most of all to the mountains which rear their glittering summits far above 
populated slopes, where no* mortal foot has yet surmounted the snow. 
Every year several of these hitherto inviolate peaks are successfully scaled 
by travelers, who point out to their friends the road they must follow in 
order to surmount them ; these small spots, elevated into the glacial re- 
gions of the air, can no longer escape the investigations of man, any more 
than the vast tracts in the arctic and antarctic zones. The English may 
lay the chief claim to the honor of having given the first impulse to the 
desire for exploring so many lofty summits. It is now a hundred and 
twenty-five years since Pocock and Wyndham discovered, so to speak, 
Mont Blanc. Since that memorable epoch, individuals of the English na- 
tion are still those who, surpassing in zeal and intrepidity the very inhab- 
itants of the Swiss Alps, and even the Savoyard, Italian, and French 
mountaineers, have made the most frequent ascents of Mont Blanc and 
the other giants of the Alps ; it is the English, too, who have investigated 
with the greatest ardor the Mer-de-Glace and the various glaciers of the 
Western continents, and have explained to us the actual topography of 
the almost unknown ranges of Pelvoux, Grand Paradis, and Viso ; it is 
they, too, who, by the foundation of the first Alpine Club, have since given 
rise to a great number of societies of the same kind in the diiferent coun- 
tries of Europe, Lastly, -they have just established at Lahore a "Hima- 
laya Club," in the hope of being able some day to surmount in turn all 
the lofty summits o:^ Central Asia, which are double the height of the Eu- 
ropean giants. 



470 • LIFE. 



CHAPTER XXI. 

RECLAMATION OF THE EARTH BY CULTIVATION. — ANCIENT AND MODERN IR- 
RIGATION. 

Long before man had made .the soil of the earth his own by science, he 
had commenced to adapt it to his use by cultivation. The various tribes 
of hunters and fishermen, like the nomad shepherds, did nothing to modi- 
fy the aspect of the earth, and if their race had become extinct, no ves- 
tige of them would have pointed out their existence on the surface of any 
continent; but as soon as families permanently settled down where veg- 
etables might be grown for food, and learned how to plant trees and to 
sow seeds and fruits, the work of transformation was inaugurated. Every 
spot of the earth where plants useful to man, such as cereals and fruit- 
trees, had taken the place of other vegetable pi'oducts which were cut 
down by the axe or cleared by burning, has become a centre round which 
cultivation has spread from place to place, till in the present time, thanks 
to the hundreds of millions of men who unceasingly labor in order to 
draw out the productive forces of the earth, immense tracts have com- 
pletely lost their primitive aspect. The total extent cultivated by the 
hand of man, and divided into fields with regular boundaries, may be es- 
timated at 2,900,0005600 acres — that is to say, about one-tenth part of the 
continental surface. It must be confessed that by far the greatest part 
of this vast tract of land is worked rather by a system of extortion than 
properly bi'ought into cultivation. 

In countries which possess soils of a naturally salubrious and fertile na- 
ture, and are not yet inhabited by a numerous population, selection is the 
only difiiculty experienced by the agriculturists, and the soil which they 
cultivate is of that kind which produces abundantly without any need of 
fertilizing it by manures. Thus, in the United States, where there are 
more than 860,000,000 acres of unoccupied ground still at the disposal of 
the citizens, the colonists cultivate little else but alluvial plains, the land* 
bordering rivers, and valleys watered by running streams. On the other 
hand, in the countries of the ancient world, where the crowded popula- 
tion is beginning to feel the want of rich soil, a great variety of soils, 
which anywhere else would be despised as unfruitful, is made to form a 
part of the domain of agriculture, and sooner or later becomes covered 
with crops. There is no soil that man, impelled by necessity, and having 
at his disposal the enormous resources which are aiforded him by the 
combined efibrts of science and industry, can not transform into fertile 
fields: by means of drainage, he draws ofi" the hurtful water which chills 
the earth and rots the roots of plants ; by means of irrigation, he brings 
on the land at the proper time the water necessary for the development 



^CULTIVATION OF THE SLOPES OF ETNA. 47 1 

of sap and tissues ; by means of manure, he enriches the soil and nour- 
ishes the growing plants ; and by these and other improvements, he 
changes the nature of the very soil. Agriculture, which was formerly 
carried on quite at random, is tending more and more to become a sci- 
ence ; and it will become a perfect science when the laws of chemistry, 
natural philosophy, meteorology, and natural history are thoroughly un- 
derstood. 

Among the great agricultural undertakings already accomplished sole- 
ly through the sheer perseverance of the peasant, without even the assist- 
ance of the resources of modern skill, there are some which are truly ad- 
mirable. For example, what could be more wonderful than the hillocks 
on the banks of the Moselle and the Rhine, or the hills of Provence, Li- 
guria, and Tuscany, which, from the base to the summit, are encircled by 
wide concentric stages, each of'which are covered with crops of vines, ol- 
ive-trees, or corn ? The "pickaxe and spade have broken up the loose 
rocks, and the debris have been used to construct this huge staircase of 
walls, each of which, like the terrace of a garden, keeps back the vegeta- 
ble soil, and prevents it from crumbling down the declivity of the rock, 
Should a storm breaking over the mountain overthrow their w^alls and 
devastate their pieces of ground, next day the peasants are to be seen 
hard at work reconstructing the stages, while others — and the women 
generally perform this task — toil up from the foot of the mountain, bring- 
ing back basketful by basketful the precious mold which had been carried 
away by the storm. How contemptible the celebrated hanging gardens 
of Babylon must appear when compared with these prodigious monuments 
of human labor ! 

The slopes of the Mediterranean volcanoes also present remarkable in- 
stances of what may be done by the persevering will of the cultivator. 
On the very sides of Etna, the summit of which rises far into the region 
of perpetual snow, more than 300,000 inhabitants have their abodes. The 
soil of the fields, which are shaded by multitudes of fruit-trees, is com- 
posed of nothing but lava and ashes; but hard and daily work has trans- 
formed it into a garden which is the wonder of Sicily. The peasants set 
stubbornly to work at every rock, and, step by step, have reclaimed them, 
and transformed their rough uneven surface into vegetable soil. When 
the mountain breaks forth into an eruption, and vomits out lava over the 
crops and the villages, agricultural labor is merely stopped for a time. 
Families religiously preserve their rights of property, just as if the prop- 
erty itself had not disappeared ; then after the lapse of few or many years, 
as soon as the cooled lava is covered here and there with patches of lich- 
ens, the agriculturist sets to work in order to utilize the smallest crevices 
of the rock which offer facilities for vegetation. Certain compact lavas, 
particularly that which destroyed a portion of Catania in 1669, can only 
be broken up by a singularly slow process, and in order to cultivate the 
upper layer of the scoria during the course of the same century, it was 
necessary to pulverize them and mix them with fertile mold ; neverthe- 



472 LIFE. 

less, industry ultimately succeeded, and gardeners planted their shoots 
of the cactus, which grew up very quickly and hid the reddish-colored 
earth behind the impenetrable thickets of their thorny leaves, which shine 
in the sun with a metallic brilliancy. Fig-trees creeping along the ground 
insinuate their long roots into the interstices of the rocks. In certain 
spots even the vine thrives and bear's fruit on these hard scoriae, which 
look almost like blocks of iron. Other kinds of lava, on account of the 
friability of their texture, and the quantity of ashes w^iich are blown on 
to them by the wind, are adapted for a rudimentary kind of cultivation 
in the space of a few years. Of this kind are the lava-flows of Zaffarana, 
which burst from the bosom of the earth in 1852 and 1853; in the hol- 
lows the inhabitants of the villages planted some brooms and furze within 
five years after the eruption.* But whether the scoriae of lava be either 
friable or hard, they will nevertheless ultimately become transformed into 
vineyards and gardens. As persevering as the ants, who seem never 
weary in rebuilding the heaps destroyed by the feet of those who walk 
over them, the peasants of Mount Etna begin again, from century to cen- 
tury, their persevering work, and, after every flow of stone which covers 
their fields, they lay out new meadows no less verdant than the gardens 
which had disappeared. 

Among all the agricultural works which have changed the aspect of the 
earth, channels of irrigation are those which, in past ages, have been the 
most magnificently planned and carried out. The Egyptians, blocked up 
by the sand of the desert, and setting their hearts, so to speak, upon the 
mud of the Nile, from which they believed their ancestors had sprung, 
made irrigation one of their great sacred rites; their reservoirs, which 
were dug out for the management of the flood-waters, must have required 
as much labor as the useless ostentatious pyramids, f In Lombardy and 
Tuscany, also, the general irrigation of the country, under the direction 
of syndicates, was practiced with great skill, and the grandest names both, 
of artists and savants, such as Leonardo da Vinci, Michael Angelo, Gali- 
leo, and Torricelli, are associated with the history of this portion of the 
art of agriculture. In the present time this work is being carried on with 
great activity in all the countries of the south of Europe, and in many 
other regions of the world which are liable to sufier from aridity. Before 
they emerge on to the plains, nearly all the mountain streams of Pied- 
mont, Provence, Roussillon, and Mediterranean Spain, are almost entirely 
drawn off on to the fields, and only during showers or the melting of the 
snow the stony beds are filled up with muddy water, which the thirsty 
land very soon absorbs. Great rivers, such as the Po, the Nile, and the 
Durance, which are utilized for irrigation, diminish in quantity of water 
every year ; and if the ambition of agriculturists is realized, they will 
ultimately disappear altogether. Love, the engineer, is desirous that all 
the rivers of France should be done away with as soon as possible by 

* Charles Lyell, Philosophical Transactions, 1858. 
t See The Earth, the chapter entitled Rivers. 



VALUE OF IRRIGATION. 473 

drawing off the tributaries at their source, and by shutting them up in 
channels for irrigation, so that they shoukl be made to follow all the 
windings of the ground.* 

Moreover, at the present day we are no longer contented with surface- 
water for the moistening of the earth. By means of boring, man seeks to 
obtain the water which flows in the depths of the earth, and to force it 
up to the surface in order to irrigate his plantations. This has been most 
successfully carried out in Algeria, either with a view of increasing the 
extent of existing oases or to create fresh ones. No doubt this operation 
mio-ht likewise succeed in other countries where underground streams are 
hidden beneath the arid soil. And this is not all ; that water which is 
diverted from its natural course or is made to gush forth from the bowels 
of the earth, acts upon plants not only by supplying them with the neces- 
sary moisture, but also by means of the various fertilizing matters and 
manures which it carries along with it. On the jields over which it flows 
it spreads the alkivium derived from formations of different natui-es, and 
thus tends to blend various soils — a process which is very advantageous 
for vegetation; by the process of "warping," it changes naturally poor 
ground, and renders it excellent for cultivation. Thus, by skillfully direct- 
ed jets of water, the Californian miners wash down high banks of sand or 
gravel in order to collect the particles of gold carried along in the stream, 
and in the same way in the Pyrenees numbers of rocky cliffs might be 
broken up into debris and be conveyed into "warping" channels, so as to 
.'^)read them in the form of an alluvium, no less precious than gold, over 
the barren sands of the Landes, This idea of Duponchel the engineer is 
certainly no mere fancy. M. Bazalgette has lately proved how far the at- 
tempt might be made to bring into being, as if by enchantment, tracts of 
fertile meadows on the unalloyed sands of the sea-shore, when watered by 
sewage brought from London more than forty miles distant. Liebig, the 
chemist, asserts that the naked sea-shore is incapable of producing a sin- 
gle blade of grass, and yet for all that it is now yielding every year six 
or seven cuttings of nutritive rye-grass,f 

* Societe des Ingenieurs Civils, Discours d'lnauguration, du 1st Janvier, 1868. 

+ M. Re'clus is evidently confusing the sewage farm in the Barking marshes vnth the hither- 
to abortive plan of reclaiming bv means of the London sewage the sands on the Essex coast. 
-(Tr.) ' • 



474 LIFE. 



CHAPTER XXII. 

THE CULTUEE OF MAESHES. — DRAINAGE OF THE GEOUND IN THE COUNTEY 

AND TOWNS. 

By means of irrigation, the agriculturist succeeds in reclaiming arid 
tracts, of land, such as the sands of the Landes, the clays of the marshes, 
and rocky cliffs ; by means of drainage, he adapts to his use flooded land 
which had never produced any thing, and converts it into the most fertile 
soil, and the name of "nursery-gardener" is now applied to those gai'den- 
ers who, in the vicinity of our large towns, are able to make the largest 
quantity of vegetable substance spring from the smallest area of ground. 
Every advance, which mankind has made either in Italy, the plains of 
France and Germany, on the saturated soil of Batavia, or in Great Brit- 
ain, would have been impossible but for the draining and sanitary im- 
provement of the ground; every spot where civilization has partially ret- 
rograded, as may be seen round Carthage, Syi'acuse, and Rome, is marked 
by fresh encroachments made by marshes once reclaimed. At the pres- 
ent time, when the work of colonization is carried out on so large a scale, 
the principal work of the pioneers in Mitidja, on the shores of the Missis- 
sippi, on the coasts of Colombia, the Guianas, and^ Brazil, in the Sundg. 
Isles, and on the coast of Africa, is to consolidate the soil and to purify 
the air, so as to add a fresh dora&in to those which mankind has already 
fully appropriated. This is a work which costs a considerable number 
of lives every year : in many a plain now rich with harvests, the number 
of peaceful agriculturists who have perished in their toil is greater than 
that of the soldiers who have fallen on fields of carnage, such as Leipsic 
or Sadowa ; but every thing gives way before patience, and sooner or 
later, thanks to the increase of the human race, to the progress of its in- 
dustry, and to the combination of its forces, the marshy banks of the 
Amazon, the lagoons of Paraguay, the wet districts of Lake Tchad, and 
the Sundej-bunds of the Ganges and Brahmapootra will ultimately be- 
come healthy countries. In all climates alike, this work of improving 
the earth is being carried on. In Norway, where the area of arable land 
was in 1866 only one thousand square miles, the agriculturists are now 
reclaiming every year forty square miles of the marshes and fjords.* 

At the present time the plan proposed by scientific men is nothing less 
than that of establishing below the surface of the ground a circulatory 
movement of waters, analogous to that which is naturally taking place 
in the air and on the surface of the earth by means of clouds and rivers. 
The water rises from the sea in the foraa of vapor, and, floating through 
space, is precipitated in the shape of rain, and returns toward the ocean 
* rrisch, Mittheilungen von Petermann, xi., 1866. 



CULTURE OF MARSHES. 475 

through streams and rivers ; but this water which is flowing down to- 
ward the great reservoir of tlie sea is, on its way, appropriated by the 
agriculturist, who divides it into channels, and then into small streamlets, 
for irrigation, and these are distributed not only on low-lying fields, but 
also on the sides of hills and mountains, and even over high plateaux. 
The water, thus being divided into innumerable bi'anches, sinks into the 
soil over the whole surface of the district, where, like a second rain, it re- 
freshes and nourishes the roots of the plants. Its work of usefulness is 
then terminated, for if it remain for any length of time in the ground its 
action will become fatal to vegetation ; it will drown and rot the small 
rootlets, and close up the jfores through which the outer air penetrates. 

Thus irrigation may be fatal where the subsoil does not possess, like 
the surface, a perfect system of channels relieving the ground of any 
superabundant moisture. The water filters, drop by drop, into the small 
drainage pipes ; then the difierent streamlets unite into one lai'ger drain, 
and gradually increasing in its course, the invisible rivulet flows from 
pipe to pipe, and discharges either into a river or into the sea. Such is 
the immense work of subterranean drainage which agriculturists are now 
undertaking in a multitude of localities ; and the result is that all the 
hydrological and climatic conditions of the soil are slowly but surely 
modified. The damp countries of civilized Europe, especially Great Brit- 
ain, are the places where the drainage of land is carried on to the greatest 
extent : in England alone the length of all the drain-pipes placed end to 
end must be estimated at not less than 6,200,000 miles, or two hundred 
and fifty times the circumference of the earth. Unfortunately the conflict 
of private interests, and the lack of enterprise and wide views in most of 
the proprietors of the soil, have prevented this work being accomplished 
according to any general plan ; each one works at it in his own field 
without troubling himself about his neighbor, and too often these partial 
systems of drainage result in swelling the streams and changing the 
lands situated below them into marshes. Sooner or later the immense 
undertaking involved in the aeration and drainage of the soil will have 
to be systematically recommenced, so as to be adapted to the whole area 
of j^very fluviatile basin. Then, and then only, shall we be able to com- 
pare the artificial system of drainage with the natural net- work of I'un- 
ning streams ; the whole of the pai'tial circulation established in each 
country by human labor will correspond with the general circulation pro- 
duced in the air and on the ground by the rotation of the globe. 

Large towns especially are the chief places where subterranean drain- 
age has in our time begun to be carried on in the most systematic man- 
ner. It is well known that rivers and streams of pure water are used in 
our towns as receptacles for all kinds of filth. If, for instance, we take 
London, that great city consisting of more than three hundred thousand 
houses, and containing more than three millions of inhabitants, which is 
connected by endless streets to numl:^rs of rising suburban towns, which 
seem to increase under your very view, and if we pass down the marshy 



476 LIFE. 

banks of the wide Thames, .which flows between such immense swarms 
of humanity, we shall see how that nation of the world, who knows best 
how to appreciate nature, also pollutes her. At the ebb of the tide, when 
the current of the river, with its slow and dark stream, flows on toward 
the sea, beds of semi-liquid mud filled with putrifying rubbish are gradu- 
ally laid bare, emitting into the air their nauseous exhalations : inspired 
by a sentiment of instinctive disgust, one is almost surprised to see the 
blue sky and the clouds reflected in these beds of moist filth. At the 
flow of the tide, when the body of water, being arrested in its progress, 
gradually rises and ascends the Thames, the islands of mud cease to be 
visible, but most of the unclean rubbish which has been borne down by 
the ebb is again carried up by the flow of the tide; a kind of to-and-fro 
motion is constantly shifting these impurities up and down stream under 
the eyes and nases of the inhabitants.* 

This is the mode in which the great river is polluted ;f the rivulets, 
and even the small streams which fall into the Thames, after having 
flowed through a portion of the province now become London, have long 
ago disappeared under the streets and the houses, and are become noth- 
ing but sewers. That which has taken place in the vast English city has 
been equally the case in all the spots where men are most densely ac- 
cumulated ; Paris has thus changed the Bievre, which flows down to it so 
pure from the hills round Versailles, into a mere ditch of liquid filth ; 
sometimes, when the water is low in the Seine, a solid mass of impurity 
may be extracted from the liquid equal to nearly a fortieth part of the 
whole flow of the river. Everywhere we find that the groups of men 
whom rivers have drawn to their banks have commenced by polluting 
the water, and have often rendered it unfit for drinking purposes, or even 
altogether injurious to health. The forcible and gross names which the 
inhabitants of the south of France have given to most of the rivulets 
which flow through their great towns, give us some indication of the 
hideous state of uncleanliness which these streams have now attained. 

Having thus deprived themselves of the drinking-water which Nature 
had placed at their disposal, although the quantity would, indeed, in most 
cases have been insufficient, the inhabitants of many towns have been c(jm- 
pelled to replace them by spring-water or streams artificially conveyed to 
them at great expense. This is one of the principal problems which we 
have to resolve in respect to the well-being of the rapidly increasing pop- 
ulations which are crowded in our great cities. In former days mighty 
Rome, who made the conquered nations of the whole earth work in her 
behalf, diverted, by means of aqueducts, the water running from all the 
adjacent mountains and made it flow down into her public squares, where 
it jetted out in abundant streams from a multitude of fountains, and was 

* Sae below, p. 477. 

t The whole of the last paragraph was evidently written without any cognizance of the pres- 
ent system of London drainage. Although this system is as yet only partially completed, the 
state of things described by M. Re'clus is now much modified. — (Tr.) 



DRAINAGE OF THE GROUND. 477 

collected in wide basins. At the present day there are very few modem 
towns which receive a quantity of water so considerable, comparatively 
speaking, as that which flowed into ancient Rome; most young and ris- 
ing cities, growing, as it Avere, at random, have not, in their foolishness, as 
yet understood what are their most imperious requirements, and are still 
deficient in the necessary supply of water. Their attention is, however, 
being more and more awakened as to this point, and the nineteenth cen- 
tury will not close before most of our large towns are abundantly pro- 
vided with all the water necessary both for drinldng purposes and for 
cleanliness. The hydraulic works of this description which have been 
already undertaken round Mavseilles, Paris, Glasgow, New York, and Chi 
cago, exceed all that the Romans have done in this respect, not by their 
beauty as works of art, but by the length and capacity of the aqueducts, 
and especially by the skill with which the engineers have succeeded in 
overcoming natural obstacles. New York is built upon an island. No 
matter ! Pure water is made to flow into it from the main-land, passing 
over the Harlem River through a gigantic arched siphon; Chicago is 
built at the mouth of a marshy river and by the side of a lake, the water 
of which is constantly polluted by the ships anchored along its shores. 
No matter ! Chicago draws its water at a point a mile and a half from 
the shore by means of a large tunnel dug under the bed of Lake Michi- 
gan : it requires a submarine stream for its daily drinking-water ! 

With regard to the discharge of sewage water — a point scarcely if at 
all less requisite than the supply of pure water — London, the greatest city 
in the world, is the one which has become the model city in this respect. 
The total length of its sewers is eighty miles, and they have been built 
large "enough to carry away from the town 2300 millions of cubic yards 
of water and filth every twenty-four hours — that is, about 28,000 cubic 
yards a second — a larger body of water than the Mississippi pours down, 
on an average, toward the Gulf of Mexico. But the efiect of these sub- 
terranean rivers is not merely to draw off the sewage water which, until 
lately, tainted the Thames ; they will soon, by means of irrigation, spread 
over more than 148,000 acres, at a distance of forty miles from London, 
and will produce grass enough to supply the requirements of 100,000 
milch-cows — many more, indeed, than is necessary to provide butter and 
milk for the whole of the immense city : " thus," states the report of the 
Board of Health, " completing the great circle of life, death, and repro- 
duction." Like some prodigious animated being, London is incessantl)' 
absorbing water by its aqueducts, and food and commodities by its rail- 
ways ; and the refuse, which it rejects and carries fer away through its 
sewers, is made available for reconstituting the nourishment necessary 
for its enormous appetite. 



478 LIFE. 



CHAPTER XXIII. 

THE DEAINING OF LAKES AND INLETS OF THE SEA, THE LAKE OF COPAIS, 

THE LAKE OF FUCINO, THE SEA OP HAAELEM, THE ZUYDER ZEE, — POL- 
ENDBRS, — THE PURIFICATION OF SALINE MARSHES, 

Emboldened by the reclamation of marshy lands, agriculture wished 
for more ; its next requirement was to t^ke possession of the beds of 
lakes, and of low grounds occasionally covered by the sea-water. From 
the earliest antiquity, great works of this kind have been undertaken ; 
twenty-two centuries ago, in the time of Alexander the Great, Krates the 
engineer devoted himself to the task of entirely emptying the Lake of 
Copais, in Boeotia, During a long series of dry years, this basin was oft- 
en reduced to a few pools of marshy water, and tiny rivulets crept oVer 
the plain between the reeds and rushes; but, on the contrary, in rainy 
seasons it was a fine lake, with an area of several millions of acres, and 
was constantly swelled by the torrents which came down from Helicon 
and the other mountains in the vicinity. The water was separated from 
the sea by a wide rampart of calcareous rocks, and found no means of out- 
let except by certain deep fissures, or ^atowo^Ara. Krates straightened 
these so as to facilitate the flow of the water; but since this epoch they 
have become again obstructed, and the projects which have been formed 
in later days for restoring the work of the ancient Greeks have beeji all 
in vain. 

Modern engineering skill has been more fortunate on the soil of Italy 
in resuming and finishing a great work of drainage which the Romans 
were not able to bring to a happy conclusion. The lake of Fucino, situ- 
ated fifty miles to the east of Rome, near the towns of Avezzano and Ce- 
lano, occupies the centre of a circular range of hills in the Apennines, 
formed like a crater, the slojDes of which are covered with dwellings and 
cultivated fields. Sometimes floods inundated all the country round and 
destroyed the crops ; and afterward, when the water ran ofi", the air was 
filled with poisonous miasmas ; the difference between the levels shown 
during high floods and at low water was not less than thirty-nine feet. 
During the reign of Claudius, 30,000 slaves worked for eleven years 
in digging out a channel 6151 feet in length across Monte Salviano, iti or- 
der to draw off" the largest portion of the water into the Liris, and thence 
into the sea. It was fully believed that the work had been happily 
achieved so as to last for centuries, like the tunnel about one-third the 
above-named length, which had been dug more than four hundred yearo 
before from the Lake Albano, near Rome. All that now remained to be 
done was to open the flood-gates. The emperor, vain as cruel, had pre- 
pared a splendid fete upon the lake ; nineteen thousand gladiators, em- 



DRAINAGE OF LAKES. 



479 











2t» 


lt,;oV\i ,l„ 


„ ~-=^^ii§^5^ 


^ 




r 



,/ 



i JVl 



.^^^4< 



-r 






* i 



i *«^ ^* V 




C^*»«a*v;lj, 




Fig. 193.— The Lake Copais. 

barked in two opposing fleets, were to* figure before him in order to cele- 
brate the inauguration of the canal. The slaughter took place; but when 
the order was given to empty the lake, the water, mixed as it was with 
blood, refused to flow out. Narcissus and some other courtiers, enriched 
at the expense of the public treasury, had doubtless kept back the money 
which was necessary to complete the works of consolidation. Later, at 
difierent periods, the canal was cleaned out, and rendered a certain 
amount of service at times. At last, in 1854, the works were energetical- 
ly resumed, the outlet was enlarged, and a mass of water amounting to 
more than a thousand millions of cubic yards, which the lake contained 
above the level of the tunnel, was emptied out, the marsh fevers ceased 
their ravages, and cultivation gradually advanced toward the centre of 
the former lake-basin. 

Among the great modern undertakings in the way of drainage, the 
most important, on account of the obstacles which had to be overcome, 
and also of the prospect which has been derived from it, is, however, that 
which has entirely recovered and added to the main-land the whole bed 
of the lake knowrt by the name of the Sea of Haarlem. This lake, as it 
appears, began to form in the thirteenth century, and since that date con- 
tinued constantly to increase at the expense of the cultivated land and 



480 



LIFE. 



villages surrounding it. In the sixteenth century it had acquired the di- 
mensions of a sea, and naval combats were fought on its waters between 
the Dutch and the Spaniards. Every great tempest added to its extent, 
and during the winter of 1836 a violent west wind caused it to reach the 
very gates of Amsterdaip. The banks round it, which were kept up at 
a great expense, were of no avail in holding back the water, which rose in- 
cessantly. Then it was that, looking forward to imminent danger caused 
by the encroachments of the sea of Haarlem, the resolution was come to 
to endeavor to drain it dry. It was thirteen miles long and six miles 




Pig. 194.— The "Polders " of Haarlem. 

broad, with an average depth of thirteen feet, and contained a body of 
water estimated at 950,000,000 of cubic yards. In addition to this, it was 
also necessary to reckon on the water resulting from infiltration and from 
rain-fall, which would make its way into the lake during the time while 
the drainage operations lasted ; this was estimated at about 260,000,000 
of cubic yards of water. In 1852 this immense work was completed, and 
three enormous steam-engines, pumping together at each stroke of the pis- 
ton as much as two hundred and sixty cubic yards of water, had dis- 
charged the whole of the sea of Haarlem into the ocean. At the present 
time, the only work the steam-engines have to do is to clear the former 



ZUTDER ZEE. 



481 



basin of the lake from the water accruing by infiltration and rain-fall, or, 
during the dry seasons, to furnish the water necessary for irrigation. In 
fact, the soil at the bed of the lake, having been for so long a time de- 
prived both of air and sun, could only be gradually changed into arable 
ground capable of absorbing easily the rain-water, and giving it back in 
the shape of vapor. It was necessary, says an author, to bring machinery 
to its aid, in order " to complete its education."* The clayey and peaty 
bed of the lake, which, since the process of emptying out and draining, 
had sunk about eleven inches, is now changed into fine cultivated lands, 
and the public wealth of Holland has been thereby increased to a very 
great extent. The emptying and drainage works- cost £1,320,000; but 
the '^ poldei's" the appearance of which, it must be confessed, is singularly 
wanting in the picturesque, already represent a value of over £6,000,000. 

Is not, however, the greater part of Holland nothing but a vast sea of 
Haarlem, which tli,e energetic and persevering people of the Low Coun- 
tries, by their labor, continued from age to age, have succeeded at last in 
laying dry ? The very sight of the level soil, every clod of which has 
been so often turned over and over, and of the defensive dikes which di- 
vide the country into an infinite number of parcels, shows how an entire 
nation — in conflict with nature and acting somewhat in the mode of a 
geological force, never ceasing for generations in its endeavors toward 
this great work — has succeeded in reconquering the soil of the country, 
and rendering it fit for cultivation. It is probable that sooner or later the 
vast gulf of the Zuyder Zee will be also recovered from the ocean. This 
work would certainly have been commenced, but for the fact that the 
greatest part of the bed of this gulf consists of fine sand, which is difficult 
to bring into cultivation. 

The ground reclaimed centuries back, either from the sea or from 
marshes, does not present any geometrical regularity in the net-work of 
its canals and draining channels. In former times the engineers were not 
so bold as they are in the present day, and, in the formation of their ca- 
nals, utilized all the small natural water-courses and passed round all the 
scarcely dried rising grounds in such a way that their ditches assume a 
winding and sometimes wavy line. As a whole, this net-work of inter- 
secting liquid veins presents a form somewhat analogous to the great and 
small vessels which follow out their ramifications in organized bodies. 
The land more recently reclaimed does not show, in its system of drain- 
age, these meandering and picturesque lines ; it is cut across by its canals 
with a mathematical regularity. At regular intervals, rectilinear and 
parallel canal* have been dug, which extend from one end to the other of 
the whole space inclosed by the dikes. These canals are crossed at right 
angles by main arteries of the same width, and thus the whole country is 
divided into great parallelograms, which are again subdivided into small 
parcels of land by narrower canals and ditches, both equally rectilinear: 
the farmer is obliged to use boats either to visit his farm, to carry his ma- 
* E. Marzy, VHydraulique, p. 235. 
31 



482 LIFE. 

nure, or load back his crops. All round this vast chess-board of culti- 
vated ground extends the canal which surrounds it and receives the drain- 
age water of the polder, being protected, by sti'ongly-made dikes, against 
inundations coming both from without and within. At one time it was 
the wind which was employed to raise the surplus water of the polder, 
and discharge it directly, or by means of canals, into some one of the 
rivers of Holland. The drainage pumps were worked by those pictur- 
esque windmills which the Dutch painters exhibit to us in all their land- 
scapes; but at the present time the larger jooMers, for which it is indis- 
pensable to assure a constant and regular flow of drainage, are pro- 
vided with steam-engines which incessantly pour water into the outside 
canal. 

When the lakes which have to be dried up are so deep that it is impos- 
sible to reclaim them for cultivation by mere ditches and canals, the only 
course left is either to empty them boldly, as the sea of Haarlem was 
emptied, or else it is necessary to work for centuries m elevating above 
the surface of the water certain small islets which will ultimately be 
joined one to another. The brave agriculturists of the Low Countries, 
feeling that the lapse of ages made them one with their descendants, did 
not shrink from undertaking this task, which would some day be com- 
pleted by their grandchildren. In the first place, they made dikes round 
the banks of the lowlands, which they could drain with compai-ative ease, 
and afterward, when the alluvium had caused a bed of mud to show it- 
self above the water, they lost no time in taking possession of it, and in 
raising, and draining it, giving to it an elongated form which would sub- 
sequently facilitate the labor of digging canals when the pool was changed 
into 2i polder. Several generations beforehand they foresaw what would 
be the general arrangement of the land, which at present lies under wa- 
ter; and every shovelful of mud that was brought up from the bed of 
the pool, every pile that was driven down into the ooze, was made to 
take its part in the continuation of the work. We are enabled to form 
some idea of the wonderful patience and methodical spirit with which the 
farmers of the Netherlands carry on their labors if we travel over the 
Zuyder polders, and numerous other districts which are now fields, al- 
though still, in part, consisting of lakes. The houses in the villages are 
built in a long circular street on the top of the dikes which surround the 
lake, and the fields, divided by canals, spread out, like the sticks of a fan, 
round the centre of a sheet of water. According, however, to the out- 
line of the lacustrine and marshy spots which are subjected to the opera- 
tion of drainage, the polders assume other shapes of equ^l regularity ; 
they form squares, stars, and concentric polygons. If seen from a balloon, 
some parts of Holland, with the innumerable gray lines of their ditches 
and canals, would recall vaguely to the mind's eye the surface of certain 
chemical bodies crystallized in radiating or parallel needles. The aston- 
ishing regulai'ity of the landscape is undisturbed, save by the masses of 
buildings in the large towns, the parks which surround them, and the 



THE ZUYDEIi POLDEE. 



483 




Fig. 195.— The Zuyder Polder. 



roads and railways crossing the canals in an oblique direction as they 
emerge from the cities. 

The Dutch are so much accustomed to recover land by means of canal- 
ization, that they often go to work in the same w^ay in cases where the 
ground might have been brought under cultivation by other processes; 
and even in the tropical climate of Java, they have transformed the en- 
virons of their cities into small editions of Holland. On the east of the 
Low Countries, the inhabitants of Friesland, Ditmarsh, and Schleswig 
have had to come in conflict with the same difiiculties, and, like the Dutch, 
have been able to triumph over them, and to convert into polders vast 
tracts of inundated ground. On the east coast of England, the shores of 
Suffolk and of Norfolk, the estuaries of the Wash and the Humber are 
bordered by fens of very great fertility; and the encroachments of agri- 



.\ 
484 LIFE. 

culture on the ocean domain take place in these districts on a very ex- 
tensive scale. In the same way, in Belgian and French Flanders, in the 
neighborhood of Ostend, Dunkirk, and Calais, the watteringhes have been 
reclaimed from the North Sea. Near Etaples, the inland sea of Ponthieu 
or Marquenterre has been changed into fine cultivated fields; and be- 
tween the mouths of the Loire and the Charente the marsh-lands are ev- 
erywhere protected by dikes and intersected by ditches, which are crossed 
by the country people, both male and female, by means of their long leap- 
ing-poles. To the south of the Gironde there are also some " small imita- 
tions of Flanders," and in the Landes the lake of Orx has been recently 
drained by the same kind of operation as that adopted in the sea of 
Haarlem. 

In Holland and all the other countries bordering on the North Sea it is 
only necessary to throw up dikes round, and to drain the marshy tracts 
by the sea-shore, and they will be converted into fertile fields, fit, after 
a few years, for any crops which the climate allows. ' On the coasts of 
the Mediterranean, Caspian, and other seas, another course has to be 
adopted. In these districts the tracts of ground which have formerly 
been inundated by salt-water always remain more or less saturated with 
salt, an^ are unfitted for any permanent course of cultivation. Thus, in- 
stead of turning them into cultivated fields, it is found better worth while 
in many spots to utilize them as salt-marshes. Thg salt-water, conducted 
from one pond to another, evaporates in the sun, and ultimately leaves on 
the bed of the last compartment a thin layer of salt, which the laborers 
collect and pile up in great pyramids on the edge of the roads. This 
manufacture assumes its chief importance on the shores of the Western 
Mediterranean : certain salt-works on the sea-shore there produce from 
ten to twenty thousand tons every year. 

What is the cause which produces the contrast between the natural fer- 
tility of the polders of Holland and the sterility of the ground recovered 
from the sea on the Mediterranean coasts? The cause must first and 
foremost be sought for in'the greater or less supply of fresh-water which 
washes the soil. On the shores of the North Sea the air is naturally 
moist, and the quantity of rain-water which is showered down upon the 
country is very considerable. The porous earth is constantly washed by 
the rain, and all the soil on the surface is gradually carried away, so that 
almost immediately they are surrounded by dikes the cultivation of the 
polders may be commenced. It must be confessed that, on the shores of 
the Mediterranean, the saline portions of the ground are likewise dissolved 
and carried into the subsoil; but in consequence of evaporation, which is 
very active in this climate, the water from the bottoni ascends gradual- 
ly through the porous earth together with the salt which it holds in so- 
lution, and then evaporates, leaving on the surface a crust, more or less 
thick, of saline matter. A reciprocating motion is thus established be- 
tween the surface and the deeper strata of the ground ; the rain causes 
the salt to descend, and evaporation caiises it to rise again, while the sea- 



f^ ALT-WORKS OF TRAPANI. 



485 




• Fig. 196.— The Salt-works of Trapaui. 

breezes add an additional thin layer of salt to that which already exists 
on the soil. Pools of almost fresh-water and a saline efflorescence cover, 
in turns, the surface of the ground ; the plants which the laborer would 
fain endeavor to cultivate are either drowned by water or else burned up 
by salt. 

Fortunately, the knowledge of the evil has led to the discovery of the 
remedy. It is found that rain carries the saline matter down into the 
subsoil, and therefore that great temporary inundations would bring about 
this result with a much greater degree of certainty. After having estab- 
lished at a suitable depth a complete system of drainage, it is only necessa- 
ry to turn for some time a branch of a stream over the land to be drained ; 
the salt in the upper stratum will immediately be dissolved and carried 
down into the subterranean conduits, being ultimately removed by this 
powerful lixiviation into an external basin, where the emptying pumps 
are worked. The frequent application of this process of washing succeeds 
at last in cleansing from all saline matter the land that was most satura- 
ted with it, and agriculture thus gain? a new and fertile field for its oper 



486 LIFE. 

ations. Moreover, this means of reclaiming low, salt tracts on the shores 
of the Mediterranean is no longer a matter of mere speculation, as it has 
already been put in practice. Not far from Saint-Gilles, on the smaller 
branch of the Rhone, certain tracts have been purified from the salt which 
they contained and converted into corn-fields. More recently immense 
tracts of land near Frontignan, once perfectly useless, have been gradu- 
ally purified by the little stream, Roubine de la Vie, which supplies pure 
water by a lateral cutting, and then lower down in its course receives 
the drainage water charged with saline matter. According to M. Du- 
pouchel, the inventor of this system of purifying the soil, it would be 
possible to deal thus with a great part of the south coast of France, and 
to create a complete border of magnificent polders, covering a surface of 
more than 250,000 acres, and representing an agricultural value of from 
twenty to thirty millions of pounds.* And what, even, would such a re- 
clamation as this be,'when compared with those which may some day be 
made in all the countries which border on the sea and on salt lakes? 

* Annales des Fonts et Chaussees, vol. ii., 1864. 



BIKES ON THE SEA-SHOIiE. 48V 



CHAPTER XXIV. 

DIKES ON THE SEA-SHOBE. — POINTS OF DEIfENSE. — POINT-DE-GEAVE. 

Throughout the whole region oi polders scattered along the coasts of 
the ocean, the immense labors undertaken with a view of draining dry 
certain tracts of land must necessarily be completed by a system of ma- 
rine fortifications, for it is necessary to defend at any cost, against the 
force of the waves and the shock of the tempest, the cultivated land 
which has been with so much difficulty reclaimed. The whole of the 
sea-boundary of Zealand, Holland, Friesland, and the other "low coun- 
tries " on the coast of the North Sea, is bordered by a continuous ram- 
part of dikes about twenty-five and thirty-five feet high, and one hundred 
and fifty to three hundred feet broad at their base. All these embank- 
ments are constructed with the utmost care, with their longer slope, on 
which the waves have to break, toward the sea ; the bank itself is armed 
against the surf by a trellis-work of posts, fascines, and even by a woven 
texture of straw, over which the waves glide, being changed into foam. 



Fig. 197.— Profile of a Sea-dike in Friesland. 

On the land side the dike has a steeper slope, and is bordered by a small 
drainage ditch, in which is collected the water, which soaks through the 
earth, or is thrown by tempests over the top of the embankment. Should 
the sea, when it is very rough, destroy one of these ramparts, a portion of 
the polders is inundated ; but at a certain distance another dik^ rises, and 
beyond this others, which keep back the flood-waters. During the contin- 
ous labor of more than a thousand years the country people, ever on the 
watch to snatch a slice of land from the ocean, have never ceased con- 
structing embankments' round every reef of mud left bare by the sea- wa- 
ter, and the defensive ramparts are thus connected all round the outside 
of the district; in some spots where the deposit of the ooze from the sea 
takes place f apidly, the districts of the interior are separated from the 
shore by a quadruple or quintuple girdle of embankments. It must be 
confessed that, on the occasion of fearful storms, the recollection of which 
ever dwells in the memory of the inhabitants,* the sea has again taken pos- 
session of wide tracts of land, in exchange for those which man has snatch- 
ed from its domain ; but at the present time the Dutch engineers, the most 

* See p. 154. 



488 



LIFE. 



experienced and most skillful in these operations, are making regular en- 
croachments on the seas surrounding them. It has been calculated that, 
on the average, the area of the Low Countries increases at the rate of seven 
acres a day, or 2470 acres a year;* this is somewhat more than a four- 
thousandth part of the whole territory. The length of the dikes placed 
end to end would extend to several thousands of miles : they much exceed 
the embankments along the- borders of the Mississipj^i and its tributaries.! 




Fig. 198.— The Dikes of Uithnizen. 

Those spots where the currents, waves, and winds blowing from the sea 
all work together to break through the shore-line are the places where 
man is compelled to show proof of the greatest perseverance and the 
most inventive genius, in his strife with the elements. In the isle of 
Sylt, on the coast of Schleswig, the idea was formed of making the sea 
itself a joint-worker in the construction of the dikes which were to stay 
its progress. All along the sea-beach palisades were set up in two par- 
allel rows, about ten or twelve yards distant from each other. During a 
tempest, the waves charged with sand dash over* the fascines, and let fall 
among the branches the sand and shingle that they carry ; the latter is 
heaped up between the two lines of palisades, and soon a long artificial 
dune is raised along the edge of the sea, affording protection to the land 
inside. Means of this kind can not, however, be successfully made use of 
on every coast, and especially on various points of the shores of Holland, 
which seem to sink down below the sea-level like a leaky ship. The town 
of Westkapelle, in Zealand, was devastated by the waves, which opened a 

* E. de Laveleye, Revue des Deux Mondes, April 1, 1 864. 
t See The Earth, the section entitled Rivers. 



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POINTS OF DEFENSE. 489 

wide iulet through the rampart of dunes on the shore. The houses were 
rebuilt farther inland, under the protection of an enormous dike which 
closes the gap between the sand-heaps; but this embankment has en- 
tailed such an enormous amount of labor in its maintenance and repair, 
that a bulwark of solid copper might have been erected at less expense,* 
In a similar way, owing to a large opening being forced between the 
dunes on the shore, the isthmus of Perren, situated on the western coast 
of the peninsula of Holland, was threatened with being swept away ; in 
this case, Amsterdam and all the shores of the Zuyder Zee would have 
been left without protection against the waves of the sea. But by means 
of various works, dikes and stake-barriers, the inhabitants ultimately suc- 
ceeded in giving solidity to the shore. At the present 'day the inhabitants 
of this part of Holland have no longer any thing to fear from the inroads 
of the sea. 

In France, Point-de-Grave, at the mouth of , the Gironde, is one of 
those spots which may most aptly be brought forward as an instance of 
the violence of the sea, and as a locality where man has to strive his 
hardest with the breakers. It is known exactly how far the sea-beach 
has shifted its position since the year 1818; at this date Point-de-Grave 
extended into the Gulf of Cordouan, 2400 feet to the north-west beyond 
its present position. Between 1818 and 1830, it receded 600 feet, or fifty 
feet each year. From 1830 to 1842, it lost annually nearly 120 feet. Be- 
tween 1842 and 1846, when the engineers were at last engaged in their 
conflict with the sea, the Avaves advanced 630 feet in their triumphant 
march — that is, more than 150 feet in one single year. Now the sound- 
ing-line shows a depth of more than five fathoms at a j^oint where the 
outline of the shore might once be seen. It has been found necessary to 
pull down, and rejbuild farther inland, all the buildings which once stood 
at the extremity of the point. The ancient fort which defended the en- 
trance of the Gironde has been demolished by the waves, and during the 
low equinoctial tides cannons may still be seen shining in the wet sand. 
In 1846, the width of the strait which separates Cordouan from the penin- 
sula of Bas-Medoc had increased exactly one-tenth in the period of twen- 
ty-eight years. 

While the sea was thus eating away the extremity of the peninsula, at 
the same time it was endeavoring to pierce into its base. At the nar- 
rowest point of the isthmus which joins the dunes of Grave to Medoc, the 
waves worked energetically in scooping out a wide bay known under the 
name of the Bay of Huttes. From 1825 to 1854, the sea-shore receded 
1140 feet. During the period of low tides, the isthmus of Huttes, which 
extends between the ocean and the salt-marshes of Verdon, was still 1320 
feet in breadth; but at the time of flood-tide this breadth was reduced 
to 960 feet, and when the waves are lashed into fury by a storm, they 
throw their foam to the very summit of the sand-banks on the narrow 
isthmus. Another five-and-twenty years of an advance as rapid as this, 
* Smallegange, Nautical Almanac, November, 1863. 



490 



LIFE, 




Fig. 199.— The Embankments of Westbapelle. 

and the Atlantic will succeed in breaking through the fragile bank of 
sand which is opposed to it by the main-land, and will overflow into the 
marshes, converting into an island the present peninsula of Grave. The 



ENCROACHMENT OF THE ,SEA. 



491 




Fig. 200.— The Embankments of Petten. 



Gironde will join the sea by a second mouth, and the present generation 
may contemplate geological phenomena similar to those which took place 
when the island of Cordouan was detached from the main-land and srad- 



492 LIFE. 

ually changed into a shoal. It was necessary to prevent this, not only as 
it would have caused the ruin of all the property on the peninsula, but 
also as a matter still much more important ; it was necessary to preserve 
for ships the precarious shelter afforded to them by the roadstead of 
Verdon, which is already too much exposed to the violence of the west 
winds, in consequence of the constant erosion of "Point-de-Grave. It was 
therefore with good reason that the resolution was adopted of entering 
into a contest with the ocean, and to arm the peninsula, by means of bul- 
warks, against its assaults. 

In order to protect the shore of the gulf, thirteen parallel jetties from 
500 to 600 feet long were constructed. These jetties were composed of 
stiff clay faced with stones firmly fixed, and were defended against the 
onset of the waves by fascines and piles; they thus offered resistance 
both by their elasticity and the cohesion of all their' parts. Neverthe- 
less, all these jetties were not strong enough to hold their own against 
the sea in stormy weather. First one gave wa}'', and then another; so it 
was resolved to construct a dike parallel to the shore of the bay of Huttes. 
During the course of the work the waves and storms often assailed the 
dike and broke through it in various spots; but the workmen, success- 
fully fighting against the billows, were able to close up the breaches, and 
to solidify those pai'ts of the bulwark which had been broken down. In 
March, 1847, after five years spent in an incessantly renewed contest be-* 
tween man and nature, the dike, 3600 feet long, was at last finished, and 
seemed to forbid the breakers any future approach to the dunes. The en- 
gineers had begun to congratulate themselves upon their work, and were 
fancying that they had vanquished the ocean, when, a few weeks after the 
works were completely finished, a terrible tempest from the south-west 
raged in the gulf against the coast of Medoc; the last jetties of the bay 
were swept away like bits of straw, and the greatest part of the enormous 
dike was broken through, carried away, and annihilated by the all-power- 
ful billows. 

In order to check the inroads of the sea, they scarcely had time to con- 
struct at the inner curve of the shore of Huttes a kind of pyramid com- 
posed of enormous blocks of concrete, each weighing several thousands 
of pou«is. The gigantic steps of this embankment presented a firm re- 
sistance to the assaults of the waves ; but as there was nothing else em- 
ployed for the defense of the shore, the ocean soon showed threatening 
signs of turning it, and continuing beyond it its work of erosion. The 
shore of the bay of Huttes receded eighty feet, and two wells which had 
been dug and lined with stone-work, in the sand of the dunes, were Jaid 
bare to their very base, and stood up like towers on the edge of the 
waves, presenting themselves as strange witnesses to show the inroads of 
the sea. The victory had been fought for by man at great cost, but the 
sea had remained the conqueror, and thousands of pounds lay peaceably 
buried under the waves. At last it was resolved that, instead of build- 
ing a mere water-wall, as had been already done, a regular breakwater 



POIXT-DE-GEAVE. 493 

should be raised to oppose the billows; this was to commence at the 
southern extremity of the bay, and to stretch across to the north, join- 
ing the immovable rocks of Saint Nicholas, In front of this rampart, 
cubic masses of concrete weighing several tons each were thrown down, 
so as to form a kind of gentle slope, the length of which was equal to ten 
times the height of the breakwater. Added to this, the wicker-work em- 
bankments, being threatened by the incessant burrowing of the teredo^ 
were gradually replaced by strong dikes in stone-work. The ocean has 
not as yet broken through this last barrier, and hopes may be entertained 
that henceforth the same respect may be shown toward it. Nevertheless, 
the waves seem inveterate for the destruction of the obstacle which re- 
strains them, and use, in turn, both force and stratagem to attain their 
end. They displace the blocks of concrete, they sweep away the sand, 
they make crevices in the masonry, and, pushing forward in every direc- 
tion their labors of sapping and mining, they untwist the fascines so care- 
fully bound together, and sometimes leap over the construction itself, and 
boldly attack the shore beyond. 

At Point-de-Grave the conflict between the sea and human power was 
scarcely less sharp. On that portion of the sea-coast which stretches 
away for a mile and three-quarters to the south of the cape, fourteen jet- 
ties, similar to those adopted in the bay of Huttes, were pushed out into 
the sea. At the point itself, instead of the jetty, there is substituted an 
embankment running out 400 feet, composed of natural and artificial blocks 
of stone dropped down into the water from trucks. The extremity of the 
embankment, which is under water, is prolonged for some distance by 
heaping up rocks, which are dropped from small vessels when the weather 
is favorable. So great, however, is the violence of the Avaves, that these 
rocks, weighing on the average two tons each, are very frequently shifted 
by the meeting of the ebb and flow of the tide, and are drifted out into 
the ofiing. When subjected to the shock of the Avaves, the embankment 
itself has sometimes cracked here and there across its whole width, and 
the workmen are from time to time obliged to reconstruct the slope, to 
till up the cracks with stone-work, and to consolidate the block* of stone 
whose equilibrium is threatened. Sometimes, also, the water hollows out 
caverns under the rocks at the base ; it is then necessary to go down at 
low tide in order to stop up the excavations, to strengthen the approaches, 
and to prevent the advance of the enemy. t 

As if enraged at the insurmountable obstacle opposed to it by the pow 
erful breakwaters at the point, the sea has spent its fury on the tongue 
of sand which extends behind the jetty. Attacking the bank on the rear, 
the waves incessantly increased the small bay of the fort in the direction 
of the river, and between 1844 and 1854, while the sea-coast remained al- 
most in a stationary condition, that which faced the Gironde receded 1600 
feet — that is to say, 160 feet a year. A few years more, and the dwin- 
dled peninsula would have been completely broken through, the light- 
house and the other buildings would have been swept away, and the 



494 LIPU. 

jetty, detached from the mam-land, would become nothing more than a 
rock beaten by the waves. It was therefore necessary at any price to 
exclude the inroad of the sea by constructing at the angle of the fort- a 
breakwater similar to that which had been already built up in the bay 
of Huttes. A breakwater has since been erected in this spot, and at last 
a period of mere surveillance has succeeded to the contest of twenty years' 
standing between man and the ocean. The works, now happily com- 
pleted, have ultimately contradicted the general superstition which attrib- 
uted to the waves a force irresistible by man. The force of oceanic bil- 
lows, like that of the aerial waves impelled by tempests, can be exactly 
estimated in tons or even in pounds ; and, in order to overcome their 
brute force, all man has to do is to oppose a superior resistance which can 
be measured by his calculations. It is, moreover, probable that a more 
profound knowledge of hydrological laws will some day enable him to 
utilize this very force which at the present time it is so difficult to resist ; 
the ebb and flow of the tide, the waves of the tempest, sometimes so ter- 
rible, will also find their work cut out for them, and their action, when 
well directed, will become an instrument in the hand of man. 



NATURAL AND AETIFICIAL COMMUNICATION. 495 



\ CHAPTER XXV. 

INfATURAL AND ARTIFICIAL WAYS OF COMMUNICATION. — SEA-SHO^S, DES- 
ERTS, AND SAVANNAS. RIVERS, CANALS, AND RAILWAYS. BRIDGES AND 

VIADUCTS. THE CUTTING THROUGH ISTHMUSES. THE SUEZ CANAL. — THE 

ISTHMUSES OF CENTRAL AMERICA. 

All the progress realized in the reclamation of the soil would have been 
impossible if nations had not been placed in mutual connection by means 
of frequent modes of communication ; commodities are thus interchanged 
between various climates, ideas become a patrimony common to all, and 
the creative intelligence of workers has been enabled to develop and in- 
crease. 

The earliest roads used by men for the purposes of travel and of con- 
veying their produce were the natural routes afforded by the shores of 
the ocean, the deserts of sand and hard clay or rock, devoid of all vegeta- 
tion, or by the level surface or gentle undulations of prairies and savan- 
nas. Thanks to these ready-made ways of communication, nations sepa- 
rated by water, forests, and mountains have been enabled to make one an- 
other's acquaintance ; but for all this, the mutual relations which they es- 
tablished remained very difficult to keep up. The sea-shores were inter- 
sected with quagmires and mouths of rivers, both dangerous to cross; 
the deserts and savannas are the abode of famine, and the traveler who 
ventures into them unprovided with food is certain to perish. After the 
lapse of thousands of years and thousands of ages, these natural routes 
still continue as dangerous as they were when they were ventured upon 
for the first time : nothing but his skill and industry has enabled man to 
create for himself safer and more commodious roads. 

The invention of rafts and boats suggested other modes of communica- 
tion between peoples; they could now avail themselves of the winding 
courses of rivers — those " moving roads." This wms an immense progress 
made in favor of intercourse between nations, for every river, with its 
tributaries, tended to connect together all the countries comprised in its 
basin ; this amount of progress was, however, in its turn surpassed. . In 
the civilized countries of Europe, where man is gradually molding Na- 
ture to his will, these uncertain water-courses, with their long windings, 
their dangerous rapids, their sudden floods, and their prolonged droughts, 
were no longer adapted either for merchants or travelers, both classes 
having become more and more particular in regard to speed and regular- 
ity. The inland navigation diminished, except on the mouths of rivers, 
whicli were also estuaries of the sea, and had been converted by the skill 
of the engineer into regular canals, having a considerable normal depth. 
This was the case as regards the Clyde, the bed of which a century ago 



496 



LIFE. 



was only three to six feet below the surface of the water : it is now duo- 
out to a depth of twenty-four feet, so that large ships can easily ascend 
the river up to the quays of Glasgow. Inland, the natural water-ways 
were abandg»ned for artificial canals, the direction and depth of which 
man could regulate at his will ; they were also, to a great extent, aban- 
doned for carriage-roads constructed across the country in every direc- 
tion, and forming an immense net-work, and for railways, ou which steam 
enabled a still greater speed to be obtained. Engineers have already 
made a demand for the suppression of our European rivers, such as the 
Loire, the Rhone, and the Rhine, as mediums of communication, and for 
the utilization of their waters for the irrigation of the land. " Rivers are 
roads for savages only," says M. Love, " and the only routes for transport 
recognized by civilized man are those which he has himself created from 






I 



Si 



-gw/'t^j<-«j[z^ 17S 8 fejg^ ; 





Fig. 201.— The Progressive Depths of tlic Clyde. 

beginning to end."* And in fact, looking at the millions of money which 
have been expended on the Loire since the commencement of the century, 
in repairing dikes, embankments, and houses, in flotillas of boats, and in 
reclaiming cultivated land, would not this cost have amply sufficed for. 
the construction of a double line of railway along the whole extent of the 
valley, and for establishing a complete system of irrigation, which would 
have changed into a vast garden all those tracts of land which are now 
constantly threatened with some calamity by the rising waters ? 

Among all the great inventions of modern times, that of railways has 
indisputably contributed the most to give an impulse to traveling, to the 
difiusion of ideas, and to the general distribution of the riches of the 
earth. The services which railways have already rendered to mankind 
are incalculable ; but nevertheless, the power 01 routine, the requirements 
of the public treasury, the impediments offered by custom-houses, the 
greedy system of monopoly and gain practiced by the various companies, 
the absence of any large comprehensive views among the constructors of 
* Discours de r inauguration a la Societe des Ingenieurs Civils, 1868. 



JRAJLWAY ROUTES. 



497 



the net-work of lines, and the troubles and disasters of war, have singular- 
ly retarded the impulse which might have been given by the iron roads 
to the activity of nations. Railways are, however, as yet, but very few in 
number, in comparison with the area of the ground which they traverse ; 
their total length is 99,360 miles — that is, about one mile only for a sur- 
face of 300 square miles. Not one of the great lines, which ought to 
cross various parts of the world from one sea to another, is as yet com- 
pleted. The longest, which commences at Cadiz, and extends for a 
length of 3700 miles, passing through Madrid, Paris, Berlin, St. Peters- 
burg, and Moscow, does not extend beyond Nijni-Novogorod, in the 
plains of Russia ; twice this length remains to be accomplished before 
the rails reach the shores of the Sea of Okhotsk. The line crossing this 
— that which extends from the coasts of Pas-du-Calais toward Constanti- 
nople — has been arrested in its progress, for more than ten years, by the 
course of the Danube. With regard to the New World, in 1869, it will 
possess a railway 3730 miles in length, which will cross the continent' 
from the Atlantic to the Pacific, from Portland and New York to San 
Francisco, and will certainly become the principal commercial art^' on 
the slobe.* 




_. 202.— The Railways of Lancashire. 

The districts where the railway system is any thing like complete are 

at present very few in number. The richest district in this respect is 

that of Lancashire, in which the first important railway — that from Man- 

* This railway is now in active operation. — (Tr.) 

32 



498 



LIFE. 



Chester to Liverpool — was opened. This is where also Stephenson start- 
ed his first locomotive. On this, the classic soil of manufactures, there 
may be reckoned at least one mile of railway for every four square miles 
of area. Also, the great facility of communication has resulted in attract- 
ing to these districts a population truly enormous, when compared with 
the small area which they occupy. In the same way London, to which 
railways converge from all the points of the compass, increases its inhab- 
itants at the rate of 60,000 a year, and in its onward march continually 
embraces within its boundary the towns, the villages, and the hamlets 
of the environs. London alone already contains nearly one-sixth of the 
population, and an attempt has been made to represent this fact in the 
diagram below, in which London, Manchester, and Liveqaool are repre- 
sented by circular areas of a size proportional to the number of their in- 
habitants. Certain thickly-populated regions in Belgium, Rhenish Prus- 
sia, and Massachusetts are also crossed by railways in *every direction ; 
but everywhere else, except in the vicinity of capital cities, the net-work 




Fig. 203.— Comparative Populations of London and England generally. 



The Ocean, &c. 



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TRA.NSALPINE RAILROADS. 499 

t 

of lines is still very far from being completed. Some continents are al- 
most entirely without this mode of rapid communication. South Ameri- 
ca, which is twice the size of Europe, does not possess more than 1800 
miles of railway. If we except Hindoostan, the only railway in the con- 
tinent of Asia is that from Smyrna to Ephesus ; Africa, also, is devoid of 
railways, except in the extreme north and south — that is, in the two colo- 
nies of Algeria and the Cape of Good Hope, and in the Nile basin, which, 
as far as commerce is concerned, is only a colony of Europe. 

During the last forty years, two thousand millions of pounds have been 
expended in various countries in the construction of railways ; and even 
this large amount is nothing but a small sum compared with that which 
it will be necessary to expend in order to continue and complete the 
work which has been undertaken. No one can fail to see that these ex- 
penses are very different from those which are employed by man in the 
art of destroying one another, and that their tendency is to create fresh 
Avealth, and to bring nations into friendly relationship. The fraction of 
national savings which is able to escape the rapacity of taxation and the 
squanderings of luxury and debauchery, although still, alas, too small an 
amount, will serve, however, to bring to a happy completion those enor- 
mous works of which our ancestors never dreamed ; and we must not 
think of styling even these works as " wonders of the world," because 
some day still greater works will be attempted. The Pyrenees, the 
Cevennes, the Vosges, the. Jura, the mountains of Bohemia, and the Apen- 
nines are already crossed by railroads ; the locomotive scales the heights 
of the Sierra Nevada of California at as great a height as 7020 feet, while 
on the east it crosses a pass of the Rocky Mountains 8240 feet high. At 
Soemmering and at Breuner, the Alps have submitted to the hand of the 
engineer; Saint Gothard, the Simplon, Mont Genevre will be surmounted 
in due course ; and finally, for the last eleven years, the work has been 
going on of driving a tunnel 13,363 yards long under the mountains of 
Frejus, between the French village of Modane and the Italian town of 
Bardonneche, while sixteen miles to the eastward a temporary railway, 
following the windings and scaling the heights of the Mont Cenis car- 
riage road, reaches an elevation of 6880 feet, and then descends in zigzags 
into the abyss at the bottom of which is situated the town of Suze. In 
the time of Hannibal and the Romans, and down to the earlier years of 
the present century, no one could travel from La Maurienne to Italy ex- 
cept by the pathways of the two Monts Cenis, or through formidable 
passes intersected by precipices, and almost always obstructed by gla- 
ciers. Since 1840, one route enabled tlie travelers of the two nations to 
communicate with one another at all seasons; and now the pressure of 
the two commercial currents which seek to be connected across the ram- 
part of the Alps has become so strong that it has been found necessary to 
improvise a railway Sa special construction, while waiting for the great 
international road which will overcome the obstacle of the Alps between 
Paris and Turin.* 

* The Mont Cenis Tunnel was opened in 1871. 



500 LIFK 

• 

The engineers who can pierce through mountains have no longer any 
fear of suspending their iron ways above the widest rivers or even over 
arms of the sea. In Canada, a viaduct nearly two miles long crosses the 
St. Lawrejjce ; not far from the falls of Niagara, a bridge carrying four 
lines of rails crosses the abyss into which the water dashes down. In 
England, the straits of Anglesea, the estuaries of the Mersey, Saltash, and 
many others, are crossed by magnificent tubular bridges ; and, sooner or 
later, the two shores of the Bosporus and of the " Phare " at Messina will 
be co^mected by bridges over which railway trains will rush. Lastly, for 
some years past engineers have been emulating one another in proposing 
to do away with the gap, presented by the straits of Dover, between the 
continental net-work of railways and those of Great Britain, either by a 
tunnel under the bed of the sea, or by constructing a bridge twenty-two 
miles long between the two cliffs. This is far from being a mere chimer- 
ical dream : the money spent in the terrible contests of Solferino or Sa- 
dowa would have amply sufficed for the execution of this work. In a 
few years skill and perseverance will have reconstructed the isthmus 
which the waves took thousands of centuries to destroy. • 

In the same way as straits are no longer allowed to arrest the progress 
of the locomotive, so isthmuses have to open out for navigation, and to 
complete the work of the remolding of the earth. The ancients formerly 
tried their hands at these great works, but their attempts never attained 
any definite result. Thus the Greeks, and after them the Romans in the 
time of Nero, commenced at various times to cut a canal between the 
two bays — one in the Ionian Sea and the other in the Archipelago — 
which are separated by the isthmus of Corinth. At the spot chosen, the 
land to be cut through was not moi'e than four miles wide, and rose from 
the two coasts in a gentle slope to a level of one hundred and ninety feet 
in height. If we take into account the small dimensions required for a 
canal intended to carry only Greek and Roman galleys, the labor of ex- 
cavation would not, at the present day, seem any thing extraordinary ; 
but the difficulties appeared insurmountable to the engineers of old, and 
the vessels which desired to pass from one gulf to the other were com- 
pelled' to make a great circuit round the promontories and isles of the 
Peloponnesus, exposed to all the dangers of the main sea. 

The navigable canal, commenced by Pharaoh Necho twenty-five centu- 
ries ago, between the course of the Nile and the Gulf of Suez, was a task 
more easy to finish successfully than cutting through the isthmus of Cor- 
inth ; for the only point in question was to make across the lowlands of 
the desert a supply channel, bringing down the fresh- water of the river to 
the Red Sea. One of the Ptolemies completed this work, which for a long 
time had. been abandoned; after some centuries of interruption. Caliph 
Omar caused it to be repaired thoroughly by his lieutenant Amrou, and 
for some years it facilitated the exchange of coiafcodities between the 
delta of the Nile and the towns of Arabia. At the present day, this 
water-road having been redug without any difficulty by the French en- 



THE SUEZ CANAL. 



501 



gineers, not only serves foi* the transport of merchandise and commodities 
between the fluvial basin and the Red Sea, but also supplies fresh-water 
to the town of Suez, the inhabitants of which have been in danger of dy- 
ing of thirst, on account of the deficiency of springs and rain-water ; it al^ 
tends to fertilize the land Avhich lies on either bank, which was formerly 
devoid of all vegetation. But this canal, although it is more useful, and 
certainly more durable, than our ancestors could ever have made it, is noth- 
ins: more than a mere detail of the mascnificent work commenced in 1864. 




Fig. 204.— The Isthmus of Comth. 

• 

The great canal, which has been in the course of construction since this 
date, and was to be terminated on the first of October, 1869, is a real arm 
of the sea ninety miles long, re-establishing the communication which for- 
merly existed between the Mediterranean and the Indian Ocean, as proved 
by the geological features of the district. The canal is deep enough to re- 
ceive ships drawing a great depth of water, and wide enough for two 
trains of boats to pass one another without difficulty; in addition, it is 
provided with vast inland ports, in which a whole fleet can be laid up, 
and with two magnificent jiorts at each end, one of which, that of Port- 
Said, is already the most roomy and safe in the whole of the Mediterra- 
nean, next to that of Marseilles. The mass of earth which it was found 
necessary to move in order to open out the route for ships is not less than 



502 LIFE. 

95,000,000 of cubic yards, so that if the rubbish was thrown up in a heap 
it would form a pyramid 31,470 feet in circumference at the base, with a 
height of 1100 feet. In consequence of the attraction which such an im- 
mense field of labor could not fail to exercise over the population of Egypt 
and of Europe generally, the desert has become inhabited, and dotted over 
with gardens and oases ; two important towns, Port-Said and Ismailia, 
have risen out of the sand ; nearly 40,000 inhabitants have established 
their dwellings in these plains, into which the traveler could not formerly 
make his way without trembling. And what will these earliest groups 
of colonists be in comparison with the multitudes which will flock from 
every quarter when Port-Said and Suez have become new Constantino- 
pies, and receive the whole or even a part of the enormous traific of 
9,000,000 of tons which, until the opening of the canal, went every year 
round the Cape of Good Hope — thus lengthening the nominal extent of 
their passage 7400 miles every voyage ? Certainly it does not seem out 
of the way to expend 12,000,000 of pounds on such an undertaking as 
this, looking at the fact that the merchants of Amsterdam, in order to 
spare their ships the short circuitous route through the Zuyder Zee and 
the passage of the Texel, have not hesitated to construct one canal fifty 
miles in length across the peninsula of Holland, and also another only fif- 
teen miles long, which have cost them not less than £2,400,000. The lat- 
ter canal cuts through the peninsula at its commencement, and crosses the 
former lagunes and marshes of the Ij, which are being rapidly changed 
into magnificent polders. 

The opening of the Suez Canal must naturally be followed sooner or 
later by a cutting through one of the isthmuses of Central America. So 
early as the year 1528, Cortez, having ascertained that no straits existed 
between the Gulf of Mexico and the Southern Ocean, applied himself to 
the means of creating one, by cutting a navigable canal through the isth- 
mus of Tehuantepec. Since the time when the former American colonies 
became free countries, and were liberated from the commercial trammels 
imposed as a right by a few houses in Seville and Cadiz, projects for cut- 
ting through the isthmuseaiiave presented themselves in lai-ge numbers — 
some laid down at hazard on merely fancy maps, and others studied with 
all the care that a knowledge of the country could suggest, and brought 
forward by men highly esteemed in science. The portion of Central 
America which engineers have vied with one another in crossing with 
their various plans for canals, either with or without locks, comprehends, 
without exception, all the narrow parts of the extensivfe district which 
joins Mexico and South Amei'ica, The isthmus of Tehuantepec and that 
of Honduras, the valley of San Juan and the narrow belt of country 
which separates the waters of the Pacific from those of the two lakes 
of Nicaragua and Munagua, the isthmus of Chirigni, the Rio Chagres 
and Panama, and Darien, the narrow stalk which connects the northern 
continent with the enormous mass of South America, have been, in their 
turns, extolled as the spots where the great commercial port of the world 



The ()('t'au.«*tc. 



ISTHMUS OF SUEZ. 



ri..x\vi 



^9" 



3o° Jiasl of Paris 



M E J) I T E R R A N E A N 




Diuwu by AVuillercaii 



Miles 

O B to to 30 



Tlie Ocean. &c. 



CENTR 







Radways constructed/ or coHStmcting 

„ „ jfTojecLedj 
TlowLc' of Canedl 



Eio^'^lTT-ErliaTd. 



HARPER &. BR 



NIERICA 



PIXWII 




Drawn ty A-VuiUeTTim . 



RS. NEW YORK 



^^' 



fti'^' 



SEIP-CANAL THROUGH CENTRAL AMERICA. 50P, 

must necessarily be opened out. According to M, Jules Flachat, the sum 
that would bei^quired for the easiest of these undertakings — that of Nic- 
aragua — would reach an amount of £'12,800,000, while the most costly 
plan — that which would take the course of the Atrato and the Truando 
— would involve an outlay of £30,000,000. This is a mere trifle com- 
pared with the treasures which are expended every year in buying war- 
like weapons and casting cannon-balls and bullets ; but it is considered a 
large amount for a work of universal interest, the result of which will be 
to bring continents closer to one another, and to hasten the day of the 
great reconciliation of nations. It is therefore possible that long years 
may still elapse before one of the American isthmuses afford a channel to 
fleets of commerce ; and yet if the sums wasted on the various financial 
markets in the promotion of fantastic joint-stock companies had been em- 
ployed in some well-grounded scheme for the junction of the two seas, 
there can be no doubt that a great part of the work would have been 
now accomplished. In Nicaragua especially, it would be comparatively an 
easy matter to open out a communication between the two oceans. The 
Spanish trading ships used at one time to ascend freely right up into the 
lake, being impelled by the trade-winds ; and even now steamboats suc- 
cessfully make head against the current of the rapids. By improving the 
port at the entrance, and by straightening the course of the San Juan in 
certain diflicult reaches, admittance to the lake could again be opened to 
ships of from 300 to 400 tons burden ; all that would then remain to be 
done would be to cut through the narrow tongue of land formed by Gra- 
nada. But to the westward of the island and the roadstead of Lapatera, 
where the vessels would be completely sheltered from the surf produced 
by the trade-winds, Maximilien de Sonnenstern, the engineer, has discov- 
ered a pass eighteen miles in length, the highest point of which does not 
rise more than twenty-three feet above the lake of Nicaragua, and about 
one hundred and forty-seven feet above the Pacific* 

* Felix Belly, A travers I'Amerique Centrale, vol. ii., p. 405. 



504 LIFE. 



CHAPTER XXVI. 

THE INDUSTEIAL POWER OP MAN, — THE ELECTRIC TELEGRAPH. —= POSSES- 
SION TAKEN OF THE SEA. CULTIVATION OP OYSTERS. 

It has been calculated by statisticians that, in the yeai" 1860, all the 
machines working in Great Britain for the benefit of manufactures gen- 
erally represented an amount of power put in force equivalent to that of 
1,200,000,000 of strong men. This considerably exceeds the collective 
force of the whole of mankind, for among the 1,300,000,000 of human be- 
ings existing, three-quarters of them are either too weak, too young, or 
too old to be adapted for any continuous labor. And yet this enormous 
total of manufacturing power in England is increasing every year at a 
rate equivalent to that of several millions of "arms-power;" in France, in 
Germany, in Italy, in the United States, in Hindoostan, China, Japan, and 
Egypt — in fact, in all the countries where civilization has introduced its 
machinery, the increase of the motive powers applied to labor in general 
is taking place in a similar or still more rapid proportion. Thanks to 
winds, water-power, steam, and other natural agents which man has en- 
listed to do his work for him, manufacturing skill every year achieves a 
task of increasing grandeur, and is incessantly contributing more actively 
to modify the aspect of our globe. 

But what are the wonders of to-day compared with those which science 
will some day give us the means, of accomplishing ? When we shall be 
enabled to lay hold of and to fetter, so as to make it work for us at our 
will, the power exercised in a limited space by the sustained blast of gne 
of the hurricanes of the West Indies; when we are enabled to employ the 
active force developed by the waves which break during a stormy winter • 
on the dikes of Cherboui-g, or even the flow of the tide which covers ev- 
ery month the shores of the Bay of Fundy ; when we know how to de- 
prive volcanoes of the terrors which they inspire, and to conciliate for our 
use the formidable power of the lava and the compressed gases which are 
at work in their abysses — what works will be so colossal that labor and 
boldness will recoil from them?* We may feai-lessly assert, that all that 
man has hitherto done is but a trifle in comparison with what he will bq| 
able to effect in the future, when the forces at his disposal, instead of neu- 
tralizing one another, will be able to work in concert. If our rude ances- 
tors, who inhabited caves during the Stone Age, were to return among us, 
they would without doubt be too ignorant to understand, or even to won- 
der at, the immense progress made since the ages of barbarism.f And 
are we ourselves at the present day sufiiciently advanced even to form an 

* George P. Marsh, Man and Nature. 
, t Grove, Address to the British Association, Nottingham, 1866. 



THE ELECTRIC TELEGRAPH. 5 05 

idea as to what the surface of the globe will be when man shall have, so 
to speak, reconstructed it, aided by the means of increasing power which 
will be furnished to him by a thorough knowledge of nature and her phe- 
nomena? 

Among the material achievements of modern science, that which gives 
us the highest hope in respect to thPfuture progress of mankind is the 
electric telegraph. By this invention man ceases to be connected merely 
with that part of the globe on which he treads so lightly, his liberty is 
set free from the obstacles imj^osed by time and space, and he becomes, as 
it were, personally present at all the points of space which the conducting 
wire brings'^nto relation with his thoughts. To the jjower of his machin- 
ery, which might be compared to muscular force, he adds the 7iervous 
forces aiForded by fibres stretching in every direction ; news, transmitted 
from cell to cell, reaches the brain of man from all the ends of the earth, 
and his expressed wishes are flashed across continents, so as to be trans- 
formed into actions on the other side of the globe. 

The construction of electric telegraphs did not commence until about 
ten years after the completion of the earliest railways ; but owing to the 
comparative simplicity of the works requisite for the establishment of 
electric wires, the total length of telegraph lines already much exceeds 
that of the iron roads. For an expense of about £20,000,000 we have 
been able to set up more than 1,300,000 miles of wires — a length which 
would reach nearly 621,000,000 of miles if we were to reckon all the dou- 
ble and multiple wires of importance ; this is an extent equal to the length 
of a string which would encircle the globe at the equator as many as 
twenty-five times. The new wires unrolled every year would be sufficient 
to give another turn of the string round the whole circumference of the 
planet; it is the far-reaching stretch of the human will which is thus ex- 
tended so far over the domain which it has made its own by its skill and 
energy. 

Not only on the surface of the main-land, but also in the depths of the 
sea, does the electric fluid transmit the thoughts of man all round the 
globe. By about fifteen wires which rest on the bed of the Channel or 
of the North Sea, Great Britain is connected with the coasts of France, 
Belgium, and Holland; Sweden and Norway are directly' joined with 
Germany by wires across the Baltic; Sicily and Sardinia have, in spite 
of the Mediterranean, become portions of the Italian main -land. We 
can still recollect with what emotion we greeted the first interchange of 
thought flashed from one side of the Atlantic to the other, passing under 
the immense body of water 2200 fathoms deep, and as broad as an eighth 
part of the circumference of the globe. These first words which the Old 
World thus sent to the New were words of peace and good- will ; it was 
understood by all that the great fraternity of man had then asserted its 
existence in a most solemn manner ; in spite of all the obstacles nature 
could offer, in spite of continents, seas, and space, widely-distant nations 
were beginning to be sensible of one common soul. After transmitting 



506 



LIFE. 






AMERICA 
NORTH 










DeodufniiuO to il}9 foUiA. iPBtmm io93 aad!/ nwrs^ 

tSS3 .^^ ^^ 

Fig. 205.— The Transatlantic Cables. 

these words of peace and scrawling some indistinct syllables, the Transat- 
lantic Cable, as if exhausted by its first efibrt, and, as it were, ceasing to 
live, refused to respond to the learned electricians who were soliciting it 
on both shores of the ocean ; silence had resumed its empire across the 
broad tract of water. But the persevering Anglo-Saxons did not suc- 
cumb to the blow of this defeat : they again manufactured thousands of 
miles of fresh wire, and commissioned their engineers and their most skill- 
ful mariners to lay it down in the bed of the ocean. Then, with an anx- 
iety as great as that experienced on the eve of a decisive battle, they wit- 
nessed the departure of their finest ship, unrolling as it went the cable 
which was to unite them to their American brethren. Fresh misfortunes 
followed : the wire broke in the open sea. No matter ; they laid down 
a third, and the mighty Great Eastern made her voyage across the At- 
lantic without ceasing for one instant to keep up a communication with 
the coast of Ireland, just as if she had left in her wake a long electric fur- 
row. At the present time two electric telegraphs connect the two oppo- 
site continents, and efibrts are being made to lay down others — between 
Lisbon and Rio Janeiro, and between Brest and New York. Lines, how- 
ever, of no very great length, especially that from France to Algeria, by 
way of the Balearic Islands, have not been successfully established in a 
permanent way, the cables having often been broken ; the cables also in 
the Eastern Mediterranean, the Red Sea, and the Indian Ocean have been 
frequently injured. A total length of 12,400 miles of telegraphic wires 
has been laid down in the bed of the sea between various parts of the 
world, its islands and peninsulas ; but there does not at present exist any 
one continuous line which belts round the whole circumference of the 
planet passing across the continental masses and the depths of the ocean. 
The longest line, that between California and Calcutta, passing through 
New York, London, Vienna, Constantinople, and Bagdad, is not less than 
12,400 miles in length. 
The great undertakings which have been already accomplished on the 



3IAy TAKES POSSESSION OF THE SEA. 507 

coasts and in the depths of the ocean justify us in asserting that man has 
taken possession of it. At the present time the sea is no longer " an in- 
superable abyss," and the mariner is able to explore almost the whole ex- 
tent of it. Nearly 200,000 ships traverse the waves between the coasts 
of the various continents and islands ; more than a million of sailors have 
made their homes on the dreaded billows, and half their lives ar^ spent 
in ships which float on the waves and are beaten by the tempest. Sea- 
voyages become more and more frequent, and the number of travelers 
who cross every year from one side of the Atlantic to the other must now 
be reckoned by hundreds of thousands ; they equal the number of passen- 
gers who travel from Great Britain to the Continent over the naiTOW wa- 
ters of the North Sea, the Straits of Dover, and the Channel. Not only 
are the natural ports afforded by the bays and river-mouths improved by 
hydraulic works of every kind, but new harbors are opened for ships on 
the most dangerous coasts. Thus the dreaded shoals yf Holyhead, King- 
ston, and Howth, and the rocky islets of Cherbourg and Plymouth, have 
been utilized as foundations for jetties and embankments, inclosing large 
areas of water, where great ships may find a safe refuge. In other places, 
as at the mouth of the Danube, the two banks of the river have been 
pushed out to a considerable distance into the sea, so as to reach deep 
water,* At Portland, the summit of a hill has been thrown over into the 
sea so as to form an immense breakwater, inclosing a whole bay, where 
fleets might safely manoeuvre. The idea has even been started of con- 
structing hSrbors in the open sea. M. Thome de Gamond has proposed 
to utilize the Varnes Bank, in the middle of the Pas-de-Calais, for estab- 
lishing a great harbor of refuge on the track traversed every year by 
more than a hundred thousand vessels. 

Another attempt at taking possession of the sea is that which has been 
made by the " farmer " of its waters. This attempt is not limited, like 
that of the hunter on the dry land, or of the fisherman on rivers and in 
the ocean, to merely catching animals in order t6 make food of them; but 
rising a degree higher in civilization, the "oyster-farmer" has learned to 
imitate pastoral nations, and instead of, like a savage, destroying living 
beings without paying any attention to the maintenance of the species, he 
makes it his business, on the contrary, to increase the number of its indi- 
viduals by rearing them, and takes care of them in order to insure his fu- 
ture subsistence. Thus the " oyster-farmers " cover their submarine fields 
with fagots, stones, and tiles, to which the " spawn " sticks — that is, the 
innumerable multitude of small organisms which will ultimately develop 
into oysters. When the mollusks, after having escaped the thousand 
causes of destruction by which they are surrounded, have attained some 
little size in the beds, they are fished up and removed to fatten in reser- 
voirs, where they reach their full growth. The fishermen of the He de 
Re, who commenced the cultivation of oysters scarcely ten years ago, 
have already established beds which extend over an area of 15,500 acres, 
* See The Earth, the section entitled Rivers. 



508 



LIFE. 



and they obtain from them more than 300,000,000 of oysters every year. 
This mollusk is also cultivated on the artificial banks of Arcachon, Ma- 
rennes, in the bay of Saint-Brieuc, and on the shores of Cotentiu. In En- 




Fiff. 206.— The Roadstead of Aiguillon. 



g.and, also, the cultivation of the oyster is assuming an increasing impor- 
tance, and is gradually taking the place of the former barbarous methods 
of fishing for them. Bnt in the United States especially oyster culture 



OYSTER AND IWHSEL VULTURE. 5O9 

lias increased enormously. Out of the 50,000,000,000 of oysters which 
are eaten every year in America and Western Europe, the share in the 
consumption taken by the United States is nearly 45,000,000,000. The 
quantities of mussels which the fishermen dredge up on the coasts and 
make articles of commerce are also most considerable. In the roadstead 
of Aiguillon alone, where the culture of this mollusk has been practiced 
ever since the thirteenth century, more than 500 fishing-hurdles or ranges 
of palisades may be reckoned, on which the mussels hang in immense clus- 
ters; the mussel-fishers collect them by millions every year ofi" one pali- 
sade only. 

The cultivation of marine plants has not yet been undertaken by man. 
All he does in this way is to collect the sea-weeds on the beach, mixed 
with fragments of shell-fish thrown up by the waves, and to utilize them 
for manuring his fields.HThis employment of sea-weed is, however, en- 
tirely local in its character, and is inconsiderable in extent. If only agri- 
culturists desire it, they can find for all the arable land in the world an 
inexhaustible quantity of manure ; to do this, all that would be necessary 
would be to send fleets to gather cargoes of sea-wrack in the interminable 
prairies of sargasso in the Atlantic and Pacific Oceans.* 

* See above, p. 371. 



510 LIFE. 



CHAPTER XXVII. 

COMPARATIVE HAEMLESSNBSS OF HUERICAISrES. — PREVISION OP WEATHER. 
MODIFICATION OF CLIMATES EFFECTED BY THE LABoll OF MAN, 

Another circumstance which singularly contributes in hastening to 
the " taking possession " of the seas, is the fact that winds and even ter- 
rible hurricanes have lost some of their power over man. Thanks to the 
previsions which science has enabled our mariners to exercise, these mete- 
oric phenomena become less and less terrific ; and their beneficent action 
in blending difierent bodies of air is no longel^accompanied, as it once 
was, by so large a number of local disasters. Guided by the appearance 
of the sky and of the sea, as well as by the oscillations of the barometer, 
the captain of a ship sees beyond the hoiizon the tempest which is ap- 
proaching, and fearlessly takes proper measures in order to avoid in good 
time the formidable cyclonic storm which is about to burst upon the sea. 
As far as regards a well-commanded steam-ship, " a huiTicane is no longer 
a possible event;" the cyclone is nothing more than an ordinary whirl- 
wind all round which a ship may sail without danger, keeping away from 
it if there is any fear of becoming entangled in the vortex, and, on the 
contrary, approaching it, if the direction of the tempest may be made fa- 
vorable to its course. The hurricane, which was the terror of navigators 
in former times, may thus become in our days a powerful auxiliary.* In 
the vicinitj^ of the coast, the danger, of course, remains very great, be- 
cause the ship has not a free space before it; therefore, when a hurricane 
is anticipated, mariners are compelled to put out as soon as j)0ssible into 
the open sea. • 

Coasts along which the navigators of the olden time used servilely to 
creep, dreading to face the terrible Neptune, are now avoided by sailors, 
for it is on the coasts, and principally on the low-lying beaches, that near- 
ly all the shipwrecks take place. The descriptive charts which are drawn 
up by the salvage societies to show the proportion of calamities occurring 
on the various points of the coasts of Great Britain and France bear wit- 
ness to the formidable nature of these dangers ; out of one hundred ves- 
sels, two on the average have to suffer disaster in each year. The seas 
which are tranquil and deep enough to enable vessels to sail at all times 
without fear in close proximity to the coast, are less numerous ; the 
shores of the Mediterranean are no less sprinkled with wrecfege than 
those of the ocean, and some of these spots, especially that portion of 
the curve which extends between Cette and Marseilles, are particularly 
dreaded. In order to diminish the number of shipwrecks, attempts have 
vefy rightly been made to improve the ports, to open harbors of refuge, 
* Bridet, Etude sur les Ouragans de V Hemisphere Austral. 



PREVENTION OF SHIPWRECKS. 



511 



to light up dangerous coasts with beacons visible at a great distance out 
at sea, t^point out shoals by means of landmarks and buoys, and to com- 
municate with mariners by means of the telegraphy of semaphores; and, 
above all, a precise knowledge of the movements of the atmosphere, en- 
abling one to form an increasingly clear prevision of the phenomena of 
I lie weather, are the means by which disasters at sea may be best pre- 
vented. Navigation, especially steam navigation, which enjoys the im- 
mense privilege of speed, will have but very few dangers to fear when 
mariners understand the art of manoeuvring in order to avoid tempests, 
and every vessel has become a floating observatory, as suggested by 
3Iaury, the illustrious American sailor. 



^^ ^ T E R 1^ 

7'/i^/i''/ure.f iimrhod o't- the- dcveiiptii&it 
the i/ir-iiiba- pf vexseij h st per jrU-l-e^' 




ffihe, wast Uldicxiie^ 
xTuircfor one yrah. 



Fig. 207. — Shipwrecks in the Mediterranean. 

At every period of history men have made it their business to en- 
deavor to foretell the weather. Owing to the numerous advantages 
which are offered us by civilization, the practical utility of knowing be- 
forehand any approaching meteorological changes has become less ur- 
gent, because in the present day we can to some extent shelter ourselves 
from the influence of these variations by our clothing, our dwellings, and 
our food. There are even some people who, by means of an altogether 
artificial mode of life, have arrived at the point of being unacquainted 
with the greater part of the meteoric agencies of the air. This was not 
the case with the nations of antiquity. Living in the open air or in ill- 
closed huts, seeking their livelihood in hunting, fishing, agriculture, or in 
rearing cattle, they wei'e compelled incessantly to search the horizon in 
order to discover the earliest antecedent signs of wind, storm, and rain. 
By a constant examination of the heavens, the most skillful observers 
were enabled to discover either more or less accurately a great number 
of facts which placed them in a position to foretell the weather ; especial- 
ly in countries where the phenomena of the atmosphere took place Avith 
some degree of regularity, as in Egypt and the Indies, those who were 
called " wise men," on account of their knowledge of times and seasons, 
learned to make fortunate prognostications as to the approaching changes 
of temperature which were not indicated to the common herd by any out- 



512 LIFE. 

ward signs. Having been converted into proverbs which were repeated 
from mouth to mouth, a great portion of these predictions have come 
down to our time, and in the different localities whei'e they were origin- 
ally uttered one may now judge of the amount of truth which they ai- 
ford. Many little known facts have been verified for thousands of years 
past by these popular sayings, and a great service would be rehdered to 
science by collecting these scattered proverbs uttered in the infancy of 
nations. 

Nevertheless, in their desire to know beforehand the various changes 
* of temperature, experience is not the only thing to which men have ap- 
pealed ; they have^ought to discover in the movements of the stars the 
future not only of the seasons, but of their own personal destinies. They 
claimed to attain to a prescience of the variations of the weather by the 
apparitions and conjunctions of distant planets, and not by the phenom- 
ena of the atmosphere itself These astrological chimeras, which more- 
over suggested to ambitious soothsayers the means of obtaining ah as- 
cendency over the minds of others by the prestige of the supernatural, 
have not as yet entirely disappeared from science, and are reproduced 
from time to time under a borrowed garb more or less scientific. With- 
out feeling ourselves compelled either to assert or to deny the influence 
exercised by the hea,venly bodies on the phenomena of the terrestrial at- 
mosphere, it is certain that, in order to attain ultimately the great end of 
foretelling the weather, it is necessary to proceed methodically by obser- 
vations of ever-increasing accuracy and completeness, made at all the 
various points of the globe. By classing all the special facts, and by dis- 
cussing them so as to give to each its just value, we shall gradually dis- 
cover the general laws which bear upon them, and then, day by day, 
draw back the curtain which is spread over the field of our sight. 

Although the resources of civilization have rendered us more independ- 
ent of the variations in the atmosphere than our ancestors were, neverthe- 
less the interests which are constantly placed in peril by unforeseen mod- 
ifications of the temperature are immense, especially as regards agricul- 
turists and sailors ; added to this, the inquirers into this subject have a 
special incentive to urge them on in their studies, in the powerful attrac- 
tion which is presented to them by the study of the laws of nature. It 
is beautiful to be able to recognize order and rhythm in what at first 
seems to be nothing but the caprice of the elements, and to trace before- 
hand in the heavens the course taken by those invisible forces, the inces- 
sant conflict of which produces all the variations of weather. Such is the 
ambition which, at the present time, may reasonably be entertained. Not 
very long ago Arago expressed a doubt whether man could be thus able 
to foresee the alterations of temperature and of meteoric agencies; but 
at the present day nearly all savants, emboldened by the grand discover- 
ies made during the last few years, are, on the contrary, full of confidence, 
and look forward to becoming at an early future masters of all the se- 
crets of the weather. In England, Admiral Fitzroy, in Holland, MM. 



MODIFICATION OF CLIMATE. 513 

• 
Buys-Ballot and Andrau, in France, M. ]\fe,rie-Davy and other meteorol- 
ogists, liave been able, owing to an attentive observation of the signs of 
the atmosphere, and a comparative study of meteorological phenomena, 
to make an attempt to predict the weather two days beforehand ; and 
more often than not their prognostications, placarded in all the ports on 
the sea-coast, have been found to be justified. M. Bulard, of the Observ- 
atory of Algiers, goes stillfurther; ife announces changes of temperature 
Aveeks and even months before they take place. Moreover, the compari- 
son of the events with the predictions can not leave any doubt in the 
mind ; following the courses taken in space by the meteoric agents, is the 
plan pursued by the observer in order to be enabled to point out before- 
hand the points where, and the time when, the aerial currents will meet, 
where and when clouds will form, wet will fall, and the tempest will 
break. When, in their daily comparisons, meteorologists will be able to 
make a free use, not only of the whole net-work of European telegraphs, 
but also of all the wires upon the earth ; when they will be cognizant 
of the various daily phenomena observed at the American stations, and 
observatories, like advanced sentinels, are established at Bermuda, the 
Azores, St. Thomas, and Havana — that is, at the various points from 
whence arise the Avinds, currents, and cyclones, which take their course 
obliquely across the Atlantic — then the prognostication of the weather 
will be placed on a sure basis. The savant will read beforehand the signs 
of the heavens, the mariner will know when he ought to remain in port, 
and the agriculturist will ascertain the best time for gathering in his 
crops. 

There is, however, a triumph still greater than that of foreseeing the 
succession of meteorological phenomena, and that is the victory obtained 
by the modification of climates. In every age, man has been incessantly 
occupied in changing them by his labors of cultivation and by the amelio- 
ration of the soil ; but this work has been carried out in an ignorant way, 
and too often the effect of man's activity has been to vitiate the air, or to 
render the alternations of heat and cold still more sudden and disagreea- 
ble. Thus towns, the temperature of which was always raised three or 
four degrees by the assemblage in them of a large number of people, are 
at the same time convei'ted into centres of pestilence, whence poisonous 
gases find their way from the lungs of one to another. In the same way, 
in other countries, the wholesale cutting down of forests which has taken 
place has resulted in disturbing the harmony of nature. The mere fact 
alone of the pioneer clearing some virgin soil effects a change in the net- 
work of isothermal, isotheral, and isochimenal lines which pass over the 
country. In several districts of Sweden, where the forests have been re- 
cently cut down, the springs at the present time commence, according to 
Absjionsen, about fifteen days later than those of the last century. In the 
United States, the vast clearings which have been made on the slopes of 
the Alleghanies appear to have reYidered the temperature more variable, 
and have caused autumn to encroach upon winter, and winter upon spring. 

33 



514 LIFE, 

* 

Generally speaking, it may be "Stated that forests, which in this respect 
may be compared to the sea, diminish the natural differences of tempera- 
ture between the various seasons, while their destruction exposes a coun- 
try to all the extremes both of cold and heat, and adds still greater vio- 
lence to the atmospheric currents. If we are to put faith in certain au- 
thors, the mistral itself, the terrible wind which swoops down upon the 
Cevennes and bi-ings desolation into "Provence, has been a scourge of man- 
kind, and has blown in its full violence only since the disappearance of 
the forests on the adjacent mountains. In the same way marsh-fevers 
and other endemic diseases have often broken o«t in a district after the 
woods, or even mere sheltering screens of trees, h'ave fallen under the axe.* 
As to the general flow of the surface waters and the climatic conditions 
which depend upon them, there is no room to doubt that the result of the 
clearing away of forests is a disturbance of the regularity of the above- 
named conditions. The rain, which by the intersected branches of the 
trees, descends drop by drop, and subsequently trickles slowly through 
the dead leaves and the net-work of roots, when the forests are destroyed, 
flows down fast upon the ground and forms temporary rivulets; instead 
of descending by subterranean sources to the lower strata and sj)ringing 
up again in fertilizing springs, it runs ofi" rapidly on the surface of the 
ground, and is lost in the streams and rivers. Up-stream the ground is 
dried up, and down-stream the body of running water is so increased, that 
floods are converted into inundations, devastating the whole country 
along the river-side ; dreadful disasters are thus brought about, similar to 
those which were caused by the Loire and the Rhone in 1856. 

But man is now able to take account of the influence which his agency 
has exercised upon climate, either by improving it or making it worse ; 
and any mischief that he has done he is able to undo. He knows that by 
again planting woods he has the power of modifying the extremes of tem- 
perature, and of equalizing the amount of rain; he knows that by devel- 
oping a system of irrigation he is able to increase the fall of moisture, as 
has been proved by the observations made in Lombardy during the last 
century ;f lastly, he can make a district healthy by draining the marshes, 
by clearing the surface of the land from decaying matter, and by modify- 
ing the various kinds of cultivation. This was the case in Tuscany, where 
the valley of the Chiana, once almost uninhabitable, into which the swal- 
low scarcely dared to venture, has been completel}'' set free from the 
marsh-miasmas by the rectification of an irregular slope, covered with 
pools and lagoons. In the same way, the marshes of the district which 
was the ancient Etruria have become much less dangei'ous to the health 
of the inhabitants since the Tuscan engineers filled up the low grounds on 
the sea-shore, and have taken care to prevent the mixture of salt and fresh 
water which took place at the mouth of the streams. The amelioration 
of the air to be breathed is the mode by which man will resolve the im- 
portant question of acclimitization ; for the only hot countries that are 
* George P. Marsh, Man and Nature. t Ibid. 



MODIFICATION OF CLIMATE. 5^5 

really unhealthy for colonists who are natives of a temperate zone, are 
the moist regions, the air of which is saturated with miasmas. Even now, 
in spite of wars and of interruptions (extending through centuries) of the 
works of improvement, ahnost the whole of Europe has been rendered 
healthy by the labor of its population ; and at the present time the same 
work is being accomplished by the inhabitants of North America, the re- 
gions of La Plata, Algeria, the Cape of Good Hope, and Hindoostan ; the 
enormous work which still remains to be done in rendering healthy the 
whole surface of the planet becomes every day easier, for now men recog- 
nize the power of association, and the means by which they can do so art' 
furnished by science. 



516 LIFE. 



CHAPTER XXVin. 

INFLUENCE OP MAN ON THE FLOEA AND FAUNA OP A COUNTRY. — EN- 

CEOACHMENT EFFECTED BY THE MOEE COMMON SPECIES. EXTENSION 

GIVEN BY AGEICULTUEE TO CEETAIN CULTIVATED SPECIES. 

The first relation of man to the various animals which surrounded him 
must necessarily have been one of conflict and destruction. The great 
battle of life was inaugurated by massacre. To eat or be eaten — this was 
the alternative, not only for man but also for the great cave bear, the At- 
tic lion, the Machairodus, and many other carnivora of past ages. There 
is no doubt that the struggle may for a long time have been indecisive, 
and perhaps in many places man may have been vanquished ; but, after 
the various chances and changes of the conflict, the terrible wild beasts 
were ultimately killed down to the very last individual. Man, being 
more subtle than these monsters, and more skillful in hiding himself and 
in surprising them, was also ingenious enough to avail himself of artificial 
weapons, clubs, pointed bones, and axes or maces of stone, and was the 
conqueror in the conflict, whole races having disappeared before him. To 
say nothing of those animals which were exterminated at some unknown 
epoch in prehistoric times^, it is probable that the Schelk of Germany* and 
the great stag of Ireland were destroyed by hunters less than ten centu- 
ries before the present era. In our own time, the bufialo, the lion, the 
rhinoceros, and the elephant are constantly giving way before the ad- 
vance of man, and sooner or later they, too, will become extinct. In 
thickly-f)opulated countries, all the wild animals are in their turn destroy- 
ed, and are replaced by beasts which we use either as slaves or compan- 
ions, such as the ox, the dog, and the horse, or those animals which, like 
the pig, are nothing more than walking masses of butchers' meat. 

There are several races of. birds the extinction of which must doubtless 
be a reproach to man ; among these we may mention the Alca impennis 
of the Faroe Isles, the Dodo of the Mauritius, the Solitaire of Reunion, 
the Lory of Rodriguez {Psittacus rodericanus)., the ^piornis of Mada- 
gascar, the twelve or fourteen species of Moas of New Zealand, the Ap- 
teryx and the Palapteryx.\ M. de Lungershausen also points out as being 
extinct, or in the course of becoming extinct, seven curious species of 
birds in the Sandwich Islands, Tahiti, New Zealand, Norfolk Island, and 
the Samoan Archipelago, which have been hunted to destruction by man, 
or by his companions the dog and the cat.J The sea-cows of Steller 
{Jihytina Stelleri), the enormous cetacece, weighing 22,000 lbs., which were 

* George P. Marsh, Man and Nature, p. 85. 

t Owen ; Ferdinand von Hochstetter, Neu-Seeland, p. 447, etc. 

t Ausland, No. 30, 1868. 



DISTURBING ACTION OF MAN. 51 7 

discovered by the geologist of that name and his companions in 1'744, and 
frequented in great numbers the coasts of Behring Straits, became com- 
pletely extinct in the course of twenty-seven years, and since 1768 not 
one of them has been seen ; not even an entire skeleton is left. The 
whale, which recently enjoyed a short respite, owing to the American war 
and the working of the petroleum springs, is now again most energetical- 
ly pursued, and soon will not find any sea where it can take refuge; the 
seals are every year slaughtered by hundreds of thousands ; the sharks 
themselves diminish in number along wilh the fish which formed their 
prey, the latter having become the spoil of the fisherman. The butchery, 
year after year, of the birds which feed upon insects has resulted in a for- 
midable increase of the nunilrous tribes of ants, termites, locusts, cater- 
pillars, etc., and in the same way the cetacem and fish which have disap- 
peared are replaced by myriads of medusm and infusoria. 

With regard to this subject, Mr. Marsh expresses an o^jinion which at 
first sight can not fail to surprise, but is none the less worthy of being 
taken into serious consideration. In his opinion, the very remarkable phe- 
nomenon of the phosphorescence of sea-water has become more frequent 
in modern times, and more beautiful than it was 2000 years ago. Homer, 
who often speaks of the " thousand voices " of the ^gean Sea, makes no 
mention of its thousand glimmerings. In the same way, the poets who 
have represented Venus as springing from the foam of the sea, and have 
peopled the "watery abodes" with so many nymphs and divinities, have 
not given us a description of the sheets of liquid gold on which, during 
the night, the bright shining goddesses were used to recline. The love 
of the Greek poets for broad day and the full light of the sun might tend 
to explain this strange silence ; but why is it that savants also have main- 
tained such a sobriety of language in describing this very extraordinary 
appearance of the phenomenon of the phosphorescent glittering of sea- 
water? Aristotle, who speaks but briefly of it, attributes this light to 
" the greasy and oily quality of the sea." ^lian, the compiler, mentions 
the gleam emitted by the sea-weed on the shore ; and Pliny, the encyclo- 
paedist, tells us that the body of a species of medusa emits a certain brill- 
iancy when it is rubbed against a piece of wood. This is a point to 
which science had reached before the observations made by Americus 
Vespuccio on the phosphorescence of tropical seas. Since this epoch, 
there is not probably a single traveler who has not remarked on the jets 
of light springing forth during the night-time round his ship, not only in 
the West Indian seas, but likewise in the Mediterranean, on the European 
coasts of the Atlantic, and near the icebergs of the Polar Ocean. If Mr. 
Marsh's ingenious hypothesis is true, those among us who walk along the 
shore or sail over the sea when the waves are, as it were, on fire, enjoy a 
spectacle much more splendid than ever was given to our forefathers to 
contemplate. This, however, would be but a poor compensation for the 
ravages which have been made by our fishermen. 

The action of man has also caused a rupture in the harmony primitive- 



518 LIFE- 

ly existing in the flora of our globe. The colossal trees in our forests are 
becoming more and more rare, and when they fall they are not replaced. 
In the United States and in Canada, the noble trees which astonished our 
first colonists have for the most part been felled ; and in more recent days, 
before the finest forests in the counties of Mariposa and Calaveras be- 
came national property, the Californian pioneers had cut down, in order 
to convert into planks, many gigantic sequoias which had attained a 
height of three hundred and eighty, three hundred and ninety, and even 
four hundred feet. This is perhaps an irreparable loss, for nature requires 
hundreds and thousands of years before, she can supply the sap necessary 
for these enormous trees, and mankind, too impatient for proper enjoy- 
ment of it, and too indifierent to the fate'ofllfuture generations, does not 
as yet sufiiciently feel the extent of its own duration, so as to induce it 
to take thought for the careful preservation of the beauty of its forests. 
The extension of the agricultural domain, and the requirements of navi- 
gation and manufactures, also result in reducing the number of trees of 
an average size. At the present time they are diminishing in number at 
the rate of millions every year. Even the toy manufactori.es, and the 
chemical match factoi'ies, to say nothing of the ship-building yards, re- 
quire whole forests for their annual consumption. To make up for this 
in all the countries of the world, herbaceous plants multiply, and are cov- 
ering areas of increasing extent. 0«e might almost fancy that man was 
jealous of natui-e, and sought to dwindle down all the products of the 
earth so that they should not surpass his own level. Even now, as the 
natui-al consequence of the struggle going on between the various vege- 
table species, those which are common to several countries tend to smoth-' 
er gradually the more feeble species which try to hold their ground in 
some more limited district. Added to this, man also contributes toward 
the destruction of the original flora by increasing the field of growth of 
the invading plants. His migrations enable him to reclaim fresh tracts 
of land, and he sows them with the seed of civilized countries ; in his 
course of cultivation, he assails the mountains, marshes, and savannas, 
where the local species have taken refuge ; by his pathways, his roads, 
and his canals, he spreads far and wide, on a soil perhaps ill adapted for 
them, the plants which surround his dwellings and grow in his fields. 
Not only in more or less extensive portions of one and the same zone do 
the vegetable species which are parasites of man increase their field of 
growth, but, at the very extremities of the world, they keep on annexing 
newly colonized lands. Just as European plants encroach on the indig- 
enous species, so do the imported animals, delighting in their new cli- 
mate, drive victoriously before them the representatives of the former lo- 
cal fauna. The pig, again become wild, has taken possession of the for- 
ests of New Zealand. The rat which once frequented the two islands 
has been pushed out by the brown rat escaped from English ships, and 
the conqueror in the strife has himself become extinct in his turn befoi'e 
the European mus tribe. The New Zealand fly carefully avoids his Eu- 



EXTENT OF CULTIVATED CROP. 51 9 

ropcan rival, who has come all round the world in order to drive him out 
from the huts of the islanders. As the Maoris sadly remark, "The white 
man's rat drives away our rat, his fly drives away our fly, his clover kills 
our ferns, and the white man will end by destroying the Maori."* One 
can well understand the despainng cry uttered by Michelet in his book 
JLa Montague : " Commonplace ideas and things will prevail !" 

Oh no ; the ideal of man is the ideal which will always prevail. As 
long as this ideal is nothing else but the mere reclamation of ground for 
cultivation, every thing will bo sacrificed to this point — the variety and 
originality of species, and all the beauty of vegetation ; but when the de- 
sire of obtaining productive crops from the earth is supplemented by that 
of adorning it and of giving to it all the splendor which ai-t adds to na- 
ture ; when agriculture, at last delivered from that fear of poverty which 
now persecutes it, and is in possession of that leisure without which it is 
nothing but a slave of hunger, will be enabled, like the amateur gardener, 
to busy itself in varying species and tastefully grouping them, and in de- 
veloping elegant or magnificent forms of vegetation, no doubt it will suc- 
ceed in materially modifying the vegetable world according to its desire, 
and in giving it, instead of its primitive originality, a new beauty which 
will respond to a sentiment of ffisthetic taste. ^ 

Taking the point of view of the distribution of species, the principal re- 
sult of agriculture has been to give a wide-spread extension to certain 
plants which are used either for the food of man or for the requirements 
of his industrial skill. The rice-plant, wheat, maize, the vine, the cotton- 
plant, the coffee-plant, each, now covers millions of acres. The various 
cereals, although much less in number when compared with the 500,000 
species of other plants, extend over an area of soil which can not be esti- 
mated at less than a fiftieth part of the surface of the earth; in some re- 
gions, as in North America, fields of corn may be seen some thousands of 
acres in extent, undulating away to the farthest horizon like lakes agi- 
tated by the wind. The plants cultivated by man have so extensively 
exceeded the limits of their natural field of growth, that, out of the one 
hundred and fifty-seven species more generally cultivated, there are seven- 
ty-two which have not yet been recognized in their wild state, and as to 
the identity of which botanists still experienco^some doubt.f Until a' 
quite recent date wheat was known only as an agricultural plant, and it 
Avas looked upon as a kind of miraculous source of wealth, when M. Ba- 
lansa found it growing spontaneously on a mountain in Asia Minor. 

Northern nations push on their cultivation c^ the ground to a point 
within the polar cii'cle and very near the extreme limit where forests are 
found to grow. On the coasts of Norway, barley, which is cultivated 
nearer to the pole than any other cereal, does not succeed with any de- 
gree of certainty in districts above 66° of latitude ; but it may be seen 
here and there, in sheltered valle5^s, almost up to the northern extremity 

* Julius Haast, von Hochstetter, Oscar Peschel, Ausland, 19th February, 1867. 
t Alph. de Candolle, Geographie Botanique Raisonnee. 



520 LIFE. 

of the Scandinavian peninsula. The most northern locality in which the 
inhabitants have found courage enough to cultivate it in spite of the cli- 
mate, is Elobaken, in 70° of latitude. In Swedish Lapland the cultivation 
of barley stops short at a point ninety miles farther south ; and yet the 
annual crops are, generally speaking, onlf^ half ripe, and the farmers have 
to dry them in kilns ; at Enontekis a satisfactory crop is not obtained oft- 
ener than once in every three years. In other northern countries which 
are not, like Scandinavia, under the influence of the Gulf Stream, barley 
can not be grown with much hope of success, except in districts situated 
considerably to the south of the polar circle. But in every spot in the 
frigid zone where any groups of civilized inhabitants have established 
themselves, in Siberia, Labrador, and Greenland, these " outcasts," as it 
wei'e, of the human race have, by dint of labor, extorted from the ground 
a few vegetables belonging to more temperate climes, such as cabbages, 
turnips, lettuces, and spinach — half-starved plants which would certainly 
refuse to live in the ice-bound soil, were it not for the indefatigable care 
of the gardener who sowed them. On the slopes of the Swiss mountains 
man has likewise carried cultivation far beyond its natural limits. In 
many valleys of the Alps, fields of rye, barley, and oats are to be seen at 
an elevation of 50(^0, 5250, and in the Val Tomanche even at a height of 
6509 feet above the level of the sea — scarcely 2300 feet below the limit of 
perpetual snow.* The highest village in La Maurienne, in Savoy, is on an 
average 5898 feet above the sea; nevertheless, the inhabitants have given 
it the name of Bonneval, inspired by a kind o£ gratitude toward the land 
watered by the mountain stream Arc. On the slopes which face the 
southern sun, the villagers indefatigably cultivate both barley and rye; 
but it must be confessed that the crops are extremely late in maturing. 
The sowing takes place in July, on fields where the snow has been melted 
by spreading on them black earth or barley stubble, and often in the 
month of August or at the beginning of September in the next year, the 
fields are still green ; fourteen months are required to ripen the harvest. 
In consequence of a truly heroic conquest effected by man's industry, cul- 
tivations on the northern slope of the Valais Alps are pushed upward to 
an elevation averaging 330 feet higher than on the southern slope, which 
is nevertheless exposed ^fp the beneficent influence of the sun; the fact is, 
that the northern population, having a smaller extent of good land at their 
disposal, exercise more assiduity in their labor than the southern farmers." 
M. Rosenthal, of Breslau, has enumerated no less than 12,000 plants em- 
ployed either as articles of*food, or for their curative virtues and their 
utility in manufactures ; but the most frequently cultivated species — 
those which supply ns with food, clothing, and all that is requisite for 
life — in the absence of which man would disappear from the earth — con- 
stitute but a very small portion of the earth's flora. Europe and West- 
ern Asia are perhaps the districts which have supplied to the human race 
the most valuable species of vegetables ; even in the times of the Chal- 
* Charles Martins, Note b, la MeUorologie de Kamtz. 



CULTIVATION OF THE CINCHONA. 521 

deans and the Pelasgi, these portions of the ancient world had bestowed 
on agriculture more than half of the treasures which she possesses. The 
Indies and the Sunda Archipelago, so rich in their vegetation, are the 
habitats of about one-fourth of the plants used in agriculture and manu- 
factures, and the remainder come to us almost entirely from South Ameri- 
ca, which, as regards the multitude of indigenous' plants, and taking its 
area into consideration, is certainly the wealthiest continent of all. There 
is only one species of high importance among cultivated* plants, the date- 
tree, which finds its origin in Northern Africa ; with regard to Australia, 
New Zealand, and the United States, none of these countries have as yet 
supplied to mankind any one plant of essential utility either for food or 
agriculture, if we except the materials requisite for the building of houses 
and ships. 

It is an evident fact that men, too much the slaves of routine in their 
course of cultivation, have as yet turned to account but a very small num- 
ber of the plants which might be useful to them; and among those that 
are cultivated with the greatest care many are species of a poisonous na- 
ture, such as opium, the betel-root, and tobacco — that odious weed the use 
of which weakens the body and stupefies the mind ! To say nothing of 
the various species of trees which have not hitherto been worked for build- 
ing purposes, how many American plants there are, neglected by or even 
unknown to botanists, which might be useful either for the food of man 
or for the cure of his maladies, either by means of their stems, their bark, 
their fruits, their flowers, their germs, or their roots ! Not long back our 
agriculturists made a most important acquisition in the- virgin forests of 
Bolivia and Peru : they have taken possession of the Peruvian bark tree 
with a view of converting it into a cultivated plant. The natives, too 
eager to avail themselves of its virtues, knew of no better plan than that 
of cutting down the tree and*peeling off its bark; they traverse the for- 
ests in search of the cinchonas.^ and when they have found them, the axe 
is at once laid to them; and in the course of a few hours these trees, which 
might have supplied numerous crops of bark throughout a whole cen- 
tury, lay despoiled upon the ground. Fortunately, Clement Markham, 
the traveler, was successful in taking up a few young plants ; and at the 
present time we have the cinchona growing in cultivated forests in Cey- 
lon, the island of Java, and on the mountain slopes of the Himalayas and 
the Nilgherry hills. 



522 LIFE. 



, CHAPTER XXIX. 

INFLUENCE OF MAN ON THE BEAUTY OF THE EARTH. DISFIGUREMENT 

AND EMBELLISHMENT OF THE LAND. THE DIVERSE ACTION OF DIFFER- 
ENT NATIONS, — THE APPRECIATION OF NATURE. — THE PROGRESS OF MAN- 
KIND. 

The action of man is so powerful an agency in draining marshes and 
lakes, in smoothing down the obstacles between different countries, and 
in modifying the primitive distribution of animal and vegetable species, 
that these very facts become of decisive importance in the changes which 
the outward surface of the globe is undergoing. This action of man may 
embellish the earth, but it may also disfigure it ; according to the m.anner 
and social condition of any nation, it conti'ibutes either to the degradation 
or glorification of nature. Man molds into his own image the country 
which he inhabits; after long centuries of reckless use of it, the barbarian 
gives to the earth he lives on an aspect of rough brutality, while by an 
intelligent system of cultivation civilization makes the country radiant 
with grace and with an impressive charm ; he may humanize it, so to 
speak, so that any stranger passing through it feels a welcome when he 
enters it, and that he may safely repose in its bosom. 

As if merely encamped, like a passing traveler, the barbarian robs the 
soil without returning to it by cultivation and thoughtful care that which 
he extorts from it ; he ultimately succeeds in completeiy devastating the 
country which he uses as his place of abode, and rendering it uninhabita- 
ble. The surface of the earth presents numerous instances of devastation 
of this kind carried on without mercy for the soil. In many a spot man 
has changed his native country into a desert, and " the grass has ceased 
to grow where he has placed his foot." A large portion of Persia, Meso- 
potamia, Idumea, and various countries of Asia Minor and Arabia, which 
used "to flow with milk and honey," and once fed a very considerable 
population, have become almost entirely sterile, and inhabited by a few 
miserable tribes, living by pillage and the most primitive style of agricul- 
ture. When the powers of Rome gave way under the attacks of barba- 
rian invaders, Italy and the adjacent provinces, exhausted by the unintel- 
ligent labor of slaves, were to a great extent changed into deserts, and 
even at the present day, after two thousand years' fallow, vast tracts of 
land, which were brought into cultivation by the Etruscans and the Liculi, 
are now useless heather or unhealthy marshes. In consequence of causes 
of a like nature, which resulted in fhe impoverishment and ruin of the Ro- 
man Empire, the New World itself has lost, in an agricultural point "of 
view, a considerable portion of its territory ; many a plantation in the 
Carolinas and in Alabama wliich was reclaimed from the vircfin forest not 



MAN'S INFLUENCE ON NATURE. 523 

more than half a century ago, has totally ceased to be productive, and is 
now nothing more than an abode for wild animals. In Brazil and Colom- 
bia, naturally the most fertile countries of the whole earth, a few years 
are sufficient for exhausting the soil by means of a system of cultivation 
Avhich is a mere robbery from it. The trees are burned down, and maize 
is sown over the ashes, and the same crop is incessantly removed year af- 
ter year, until it is smothered by a fresh growth of brush-wood. This is 
burned for the second time, and maize is sown again. Ultimately ferns 
and a slimy, fetid sort of grass, called Caphn gordura, make their appear- 
ance, and the land is then destroyed for the purposes of cultivation. 

The question as to how far the agency of man serves either to adorn 
or degrade the aspect of nature may seem an idle one to minds of a so- 
called positive tendency ; but it none the less assumes an importance of 
the highest order. The development of mankind is bound up most inti- 
mately with the surrounding conditions of nature. A hidden harmony 
springs up between the land and the nation which is nourished by it ; and 
if any society is imprudent enough to lay a disturbing hand on the ele- 
ments which form the beauty of its territory, it is ultimately sure to re- 
pent of it. In a spot where the country is disfigured, and where all the 
grace of poetry has disappeared from the landscape, imagination dies out, 
and the mind is impoverished ; a spirit of routine and sei'vility takes pos- 
session of the soul, and leads it on to torpor and to death. Among the 
causes which, in the history of mankind, have eifected the extinction of so 
many forms of civilization, we must place in the first order the reckless 
violence with which most nations have treated the soil which nourished 
them. They cut down the forests, exhausted the springs, and made the 
rivers overflow, and, after thus injuring the climate, surrounded their towns 
with a belt of marshy and unhealthy land; and then, when the nature 
which they profaned showed its hostility against them, they began to 
hate it, and being unable, like the savage, to fall back on forest-life, they 
allowed themselves to fall into deeper and deeper degradation through 
the despotism of priests and kings. " Vast domains have been the de- 
struction of Italy," is the opinion of Pliny ; but it must be added that 
these vast domains, being cultivated by the hands of slaves, had disfig- 
ured the land like a leprosy. Historians have been struck with the ex- 
treme decadences of Spain since the days of Charles V., and have endeav- 
ored to explain it in various ways. In the opinion of some, the chief 
cause of the ruin which has befallen the nation was the discovery of gold 
in America ; in the opinion of others, the cause was the religious terror or- 
ganized by the " holy brotherhood " of the Inquisition, the expulsion of 
the Jews and Moors, or the sanguinary auto-da-fe of heretics. The fall 
of Spain has also been attributed to the iniquitous impost of the alcabala^ 
and to the system adopted from the French of despotic centralization. 
But is not the kind of madness with which the Spaniards have felled the 
trees for fear of the small birds, '■'' jyor tniedo de los pojaritos^'' a point to 
be considered in this terrible decadence? The land has become yellow. 



524 LIFl^- 

stony, and bare, and has assumed a repulsive and frightful aspect ; the 
soil is impoverished, and the population, which for two centuries has been 
diminishing, has partially relapsed into barbarism. The small birds are 
well avenged. 

Even in our own days, and among nations the most advanced in civili- 
zation, numbers of the works of man have been attended with the fatal 
result of impoverishing the soil and disfiguring the face of nature. Taken 
as a whole, mankind has hot yet emerged from his primitive barbarism. 
The work of deterioration assumes a diiferent aspect among different na- 
tions, according to their systems of agriculture, the variety of climates, and 
the diversity of manners and of national character. Arabs, Spaniards, and 
Spanish-Americans completely fell the trees, and leave the face of the coun- 
tiy to dry up and become yellow in the sun ; Italians and Germaris, on the 
other hand, scandalously mutilate the trees which they do not cut down, 
and give them the aspect of posts or broomsticks; the French divide their 
land into innumerable parcels, producing different kinds of crops, which, 
looked at from a distance on the hill-sides, resemble many-colored dra- 
peries spread upon the soil. In the United States the land is cut up into 
geometrical squares, all uniform and with similar bearings, in spite of the 
undulations and risings of the ground. Lastly, in some countries the pro- 
prietors of land, either poor peasants or great lords, surround their do- 
mains with defensive walls and hem them in with ditches, as if they were 
besieged fortresses. This is done even by the miserable Irishman, the 
poorest among men, who incloses with a high earthen bank his bit of gar- 
den-ground containing nothing but ill-growing plants. How many coun- 
tries there are in Europe through which one may travel for whole hours 
without finding a single spot on which an artist's glance might rest with 
any degree of satisfaction ! 

There are others besides the " rough tiller of the soil," so jealous of his 
patrimonial landmarks, and so pre-eminently eager to obtain abundant 
products, who are often at work in disfiguring the aspect of the land in 
which they live ; indeed, some of those who profess the greatest admira- 
tion for nature are in the habit of systematically degrading the most 
beautiful sites. In the environs of towns, the districts supposed to be 
country are cut uj) into inclosures, and are only represented by closely 
shorn shrubs and beds of flowers, of which a glimpse may be obtained 
through iron railings. Many of the German princelings, vitiated by a 
foolish sentimentalism, have defaced the most charming landscapes by 
carving pedantic inscriptions on the rocks, by adorning their lawns wath 
fanciful tombs, and by making their soldiers mount guard in front of the 
points of view which they desire to point out to strangers. Multitudes 
of French bourgeois^ in their mean love for a cramped and symmeti'ical 
style, have gone so far as to check the rise of the sap in the trunks, in or- 
der to create dwarf varieties, and to give to trees geometrical forms or 
the fantastic appearance of monsters and demons. The grave Dutch 
merchants of the last century were not satisfied with their garden-walks 



DISFIGUREMENTS AND EMBELLISHMENTS. 525 

unless they were edged with lime-trees having their heads clijaped into 
the shape of a ball and their trunks colored white; and the trees at 
Brouck are still painted wilh oils and zinc-white. The gardeners of the 
Emj^eror Yang-ty were in the habit of replacing the flowers and leaves 
■which fall from the trees by artificial foliage and flowers made of silk, the 
latter being impregnated with perfume, so as to render the illusion more 
complete.* 

And how far do the highest aspects of nature find their due recognition 
among us? On the sea-coast, our most picturesque clifis and our most 
charming shores are in many localities monopolized either by jealous pro- 
prietors, or by speculators who appreciate the beauties of nature in much 
the same way as a money-changer values an ingot of gold. In much fre- 
quented mountain districts a similar rage for appropriation takes posses- 
sion of the inhabitants ; the landscapes are cut up into squares and sold 
to the highest bidders ; every natural curiosity, the rock, the cave, the 
Avatei"-fall, the glacier, every thing, down even to the sound of an echo, 
may become private property. The very cataracts .are farmed out to 
contractors, who surround them with wooden fences in order to prevent 
non-paying travelers from contemplating the tumult of the waters, and 
then, by dint of laudatory articles in the public press, coin, as it were, the 
very light which plays in the broken water-drops, and the break of the 
wind which spreads clouds of mist over the abyss, and convert them into 
hard ready cash. No traveler can fail to experience a feeling of deep 
mortification when he compares the Niagara of to-day, such as men have 
made it, with the former " thunder of the waters," when it was left in the 
simplicity in which nature gave it to us. Hideous buildings, mills, work- 
shops, hotels, and warehouses have taken root on the clifls ; advertisers, 
speculating on the beauty of Niagara for the sale of their merchandise 
or of their drugs, have posted up their dirty and lying placards in front 
of the roaring cataract ; other persons, still more disagreeable in their 
ingenuity, have vainly attempted to add some poetical features to the 
scenery by erecting Chinese kiosks and Gothic turrets. The trees and 
their verdure, which formed so appropriate a frame-work to the white 
hue of the water, have fallen under the stroke of the axe, and the body of 
water itself is diminishing every day, owing to the side channels which 
are dug by the mill-owners to draw water from the Niagara for driving 
their machinery. Let the energy of man utilize, if it will, the immense 
power of the cataract ; nothing can be more advantageous ! But in this 
work of improvement the beauty of the spot has not been respected. 

This depravity of taste, which impels men to deface the most lovely 
scenery, finds its origin in ignorance and vanity, and is henceforth con- 
demned by the verdict of mankind ; the mind of man now seeks for beau- 
ty, not in vain and purel}'^ outward imitations or in a fantastic and false 
style of decoration, but in the intimate and deeply-seated harmony of his 
work with that of nature. The man who really loves the land in which 
* Meyer, Die schone Gartenkunst. 



526 LIFE. 

he lives knows that his duty is to preserve, or even to increase, the beauty 
which it possesses ; but if a reckless system has defaced that beauty, then 
it is incumbent on him to endeavor to restore it. Comprehending the 
fact that his own personal interest is blended with the interest of all 
around him, he will repair the injuries committed by his predecessors, he 
will assist the soil instead of inveterately forcing it, and will work hard 
for the beautification as well as the improvement of his domain. He will 
not only know, in his position as an agriculturist and a manufacturer, how 
to utilize the products and forces of the globe, but he will also learn with 
an artistic eye to give an additional grace and majesty to the scenery 
which is most charming. Having become " the conscience of the earth " 
by that very fact, man assumes a responsibility as regards the harmony 
and beauty of nature around him. 

Under the rude hands of the conquerors of Rome and during the un- 
happy period of the Middle Ages, the thousands of slaves who cultivated 
the soil were but little able to comprehend the beauty of the land on 
which their miserable lives were spent; and any sentiment that inspired 
them with respect for the scenery which surrounded them must necessa- 
rily have been of a vitiated character. The bitterness of existence must 
then have been much too intense for them to experience any pleasure in 
admiring the passing clouds, the rocks, and the trees. Then on every 
side were quarrels, hatreds, sudden terrors, wars, and famines. The ca- 
price and cruelty of the master was the law of the enslaved; in every 
unknown face they seemed to recognize a murderer ; the names of stran- 
ger and enemy were then synonymous. In a society of this kind, if a 
brave man wished to combat his destiny and to preserve the self-con- 
sciousness of his own soul, the only thing he could do was to be joyous 
and ironical,to scoff at the strong, and especially at his master ; but if he 
contemplated the earth, nothing remained for him but grief The splen- 
dor of the loveliest features of nature which surrounded them could not 
but remain unknown to the men who, influenced by a vague terror, sedu- 
lously kept up by sorcerers of every kind, ever fancied that, in every cave, 
in every deeply-hollowed road, in the mountain gorge, and in the dim si- 
lence of the woods, they could discern hideous ghosts and horrible mon- 
sters, partaking of the natui-es both of the beast and the demon. What 
strange ideas must have been entertained of the earth and its beauties 
by those monks of the Middle Ages who, in their maps of the world, were 
always in the habit of drawing, by the side of the name of every distant 
country, strange animals vomiting out fire, men furnished with horses' 
hoofs or fishes' tails, griffins with the heads of rams or bulls, flying drag- 
ons, and headless bodies, with wild, staring eyes placed in the middle of 
their breasts !* 

When the incessant warfare of the Middle Ages had come to an end, 
the desire of every man who had escaped in the conflict must have been 
to secure for himself some charming and sheltered home ; the bolder fea- 
tures of nature only produced fear, and all he asked for was peace. The 



TRUE ArPRECIATION OF NATURE. 527 

ideal of the generations which followed one another from the Renaissance 
to the French Kevolution is betrayed by the character of the sites cliosen 
by both princes and lords for building their country seats. But a very 
small number of these palaces occupy a position wliicli affords a view of 
a magnificent horizon of mountains and rocks ; in many localities, espe- 
ciall}^ on the shores of the lake of Geneva, the counti-y houses built by the 
rich proprietors of the adjacent land turn their backs to the scenery which' 
UOAV appears to us the grandest. Instead of an aspect of nature too im- 
pressive and too wild for him to take pleasure in contemplating it, man 
then preferred a limited area of view which the imagination could easily 
embrace, such as a curtain of gently sloping hills, a little stream winding 
along under the shade of alders and weej)ing willows, charming avenues 
of clustering trees, and lawns and lakes ornamented by statuary. They 
valued these elegant graces far above the magnificent simplicity of a 
widely extending prospect. 

The nations who at the present day are placed, in consequence of their 
jire-eminence in civilization, in the front rank of mankind, take, generally 
sj)eaking, but very little trouble in the embellishment of nature. Being 
much more devoted to industrial than artistic skill, they prefer power to 
beauty. The universal wish of man is to adapt the earth to his require- 
ments, and to take complete possession of it in order to derive from it its 
immense treasures. He covers it with a net-work of roads, railways, and 
telegraphic wires ; he fertilizes its deserts, and makes himself master of 
its rivers ; he breaks up the rising grounds, and spreads tliem in the form 
of alluvium over the plains; bores through the Alps and the Andes, and, 
having united the Red Sea with the Mediterranean, is preparing to min- 
gle the waters of the Pacific with those of the West Indian seas. Nearly 
all men, being either agents in, or witnesses of, these vast undertakings, 
allow themselves to be carried away by the fascination of labor, and 
their only idea is how they can mold the earth into the image which 
suits them best. And yet, when man forms some loftier ideal as regards 
his action on the earth, he always perfectly succeeds in improving its sur- 
face, although he allows the scenery to retain its natural beauty. Na- 
ture preserves its beauty when the really intelligent agriculturist gives 
up raising and forcing, as if at hap-hazard, plants of the most various 
kinds on a soil the properties of which he is ignorant, when, before in- 
trusting to cultivation, he first and foremdst comprehends that the land 
must not be recklessly dealt with, and previously humors it by finding 
out the crops best suited for it. Thus the "Shakers" in the United 
States, who have made agricultural labor " a ceremony of love," and feel 
it a duty to cherish the trees which they rear, the seed which they cast 
into the furrows, and the rivulet which they turn to their purpose, have 
really succeeded in converting into perfect paradises their estates at 
Mount Lebanon, Hancock, and Watervliet.* England is the country 
in which the agriculturists produce from their fields the most abundant 
* Hepworth Dixon, New America. 



528 LIFl^- 

crops, but yet its people have always shown more respect for trees than 
was ever the case with the Latin races, and there also we find but few 
localities which do not possess a certain amount of grace or even of real 
beauty, owing either to the great oaks standing by themselves and 
spreading their branches over the meadows, or to the clumps of trees of 
various kinds dotted about with picturesque art round villages and coun- 
try houses. The art of man, notwithstanding the opinion of some morose 
minds, has it in its power to embellish even the aspect of free nature, by 
giving it the charm of prospect and variety, and, above all, by placing it 
in harmony with the deepest seated feelings of those who inhabit it. In 
Switzerland, on the shores of the great lakes, and in front of blue mounl^i 
ains and glittering glaciers, how many instances there are, both of farm- 
houses and villas, which, by their grassy lawns, their clumps of flower- 
beds, and their shady walks, render the face of nature still naore beauti- 
ful, and charm, as if by some pleasant dream of happiness, the traveler 
who passes by ! . 

At the present time, the freedom from prejudice which science gives, 
the love of liberty which is spreading far and wide, the feeling of solidar- 
ity which often influences us without our knowledge, and teaches us the 
fact that the earth belongs to all, have singularly enlarged the breadth of 
view taken by man. At the same time, the increase of traveling is reveal- 
ing more and more the beauty of the earth and the harmony of its agen- 
cies. For a few years past especially, there has been springing up a per- 
fect enthusiasm in the feeling of love with which men, eminent in art and 
science, regard nature. Travelei'S spread in swarms over all countries 
which are easy of access, and remarkable for the beauty of their scenery 
or for the charm of their climate. Multitudes of painters, sketchers, and 
photographers are traversing the whole earth frorn the banks of the Yang. 
tse-kiang to those of the Amazon ; they study the land, the sea, and the 
forests in all their most varied aspects ; they exhibit to us all the magnifi- 
cent scenes on the globe which we inhabit ; and in consequence of their 
being brought more and more into intimate communion with nature, and 
of the works of art brought back from their innumerable voyages and 
ti-avels, all men of cultivation can now form an acquaintance with the 
features and aspect of the different countries of the globe. The class of 
savants, although less numerous than that of the artists, are still more 
useful in their labors of discovery, and have also become wanderers over 
the earth, and the whole world now forms their sphere of study. It was 
while ti-aveling from the Andes to the Altai that Humboldt composed his 
admirable Tableaux de la Nature, dedicated, as he says, "To those who, 
impelled by the love of liberty, have been able to tear themselves away 
from the troublesome waves of life." 

Henceforth, owing to these travels, the globe itself will become the 
agent in ennobling the taste of its inhabitants, and in communicating to 
them the sense of the truly beautiful. Those who traverse the Pyrenees, 
the Alps, or the Himalayas, or even the high cliffs along the sea-shore, 



THE PROGRESS OF MANKIND. 529 

those who phiuge into the depths of the virgin forest or look down into 
a volcanic crater, learn, while looking at these magnificent sights, how to' 
appreciate the true beauty of less striking scenery, and when they have 
the power of modifying it they will not fail to respect its peculiar fea- 
tures. We must, therefore, wish every success to that noble passion which 
impels so many men, and, we must add, the best among men, to penetrate 
into virgin forests, to traverse sea-shores and mountain gorges, and to ex- 
amine nature in all the regions of the globe where she has preserved her 
primitive beauty. It is now felt that, unless we wish to subside into in- 
tellectual and moral weakness, it is necessary that the vulgarity of so 
many ugly and commonplace things, in which narrow-minded people 
think that they discern the evidences of modern civilization, should be 
counterbalanced at any cost by the contemplation of the magnificent 
scenery of the earth. It is necessary that the direct study of nature and 
the consideration of its phenomena should become one of the principal el- 
ements of education for every cultivated man ; it is also necessary that 
skill and muscular energy should be developed in every individual, so 
that he may be able cheerfully to scale the highest mountain peaks and 
look (^own into their abysses without fear, and also to keep up in the 
whole of his physical being that natural balance of power, without which 
the noblest prospects are surveyed only through a veil, as it were, of sad- 
ness and melancholy. The man of modern times ought to combine in his 
own proper jierson all the virtues of those who have gone before him on 
the earth ; without surrendering any of the enormous privileges intrusted 
to him by civilization, it is his duty also to maintain unimpaired all the 
vigor bequeathed to him, and not to allow himself to be excelled by any 
savage on the earth in strength, skill, or a knowledge of the ijhenomena 
.of nature. In the grand times of the old Greek republics, the great ob- 
ject which the Hellenes had in view in the education of their children 
was to turn them into heroes by means of grace, strength, and courage; 
and in like manner, by stimulating all manly qualities in the rising gener- 
ation, by bringing them face to face with nature, and by leaving them to 
fight out the battle with her, modern societies of men may insure them- 
selves against the occurrence of any decadence by the regeneration of the 
very race itself 

A robust education of this kind will give us the grandest development 
of the real love for nature. Slavery and a spirit of routine may vitiate it, 
but knowledge and liberty give it new life. Science, which. is gradually 
converting the globe into one great organism always at work for the bene- 
fit of mankind, doing this by means of winds and currents, steam and the 
electric fluid, is at the same time pointing out to us the means for beau- 
tifying the surface of the earth, and for making it that pleasant garden 
which has been dreamed of by poets in all ages. Nevertheless, although 
science may bring before our eyes the distant future of a glorified earth, 
she alone can not bring to perfection this great work. A moral progress 
must necessarily correspond with this progress in knowledge. While men 

34 



530 LIFE. 

are fighting with one another with the aim of shifting the patrimonial 
boundaries and the imaginary frontiers of their nations, while the soil 
which nourishes them continues to be reddened by the blood of insensate 
wretches who wage war either for a paltry strip of territory or for some 
question of so-called honor, or incited by a mere lust for conflict like the 
barbarians of ancient times, so^ long will be deferred that paradise on earth 
which the mind's ^eye of the seeker already seems to contemplate in the 
distant future. The features of the globe will never assume their jierfect 
harmony until men are united in one league of justice and of peace. Ere 
she can become truly beauteous, our " beneficent mother " must wait until 
her sons have all embraced as brothers, and have succeeded in establish- 
ing the grand confederation of free nations. 



INDEX. 



Acotyledons or cryptogams, 357. 

"Adam's ice,"4S. 

Adriatic: sea-breezes of the, 240 ; soundings in tlie, 
24. 

Aerolites, combustion of, 209. 

Afi'icau railways, 499. 

Agriculture, 470 et seq. 

, mother of civilization, 450. 

Air, the, or atmosphere : composition of, 206 ; trav- 
els without cessation, 207 ; vehicle of all sounds, 
210; beautifies all nature, 210; the mirage, 210; 
weight of, 213 ; pressure of, 213 ; height of upper 
strata, 213 ; first measurement of weight, 214 ; as- 
cent of mountains, 214; ascent of balloons, 215; 
mean pressure of, 217; barometric variations, 219- 
222. See also Winds. 

Algffi, 390. 

Altitudes, tested by boiling water, 214. 

Amazon, fish in the river, 412. # 

, the bore in the, 119. 

America, colonization of, 405. 

, discovered by the Chinese, 87. 

American railways, 499. 

Animal and vegetable life, union of, 406. ■ 

Animals: number of species, 393; relative abun- 
dance of, 395. 

Anne, English brig, surrounded by icebergs, 53. 

Antarctic ice-fields, 55. 

Anticosti, origin of the island of, ISO. 

Antilles, origin of the, 182. 

Aracan, or hurricane, 251. 

Arboreal vegetation, limits of, 359. 

Archipelago, depth of water in the Eastern, 31. 

Areas of habitation, 408. 

Argostoli, marine streams of, 146. 

Aristotle, manner of his death, 123. 

Arsenic, found in sea-water, 30. 

Ascents of mountains, 409. 

Ashes, showers of, 228. 

Asiatic railways, 499. 

Atlantic Ocean : depth of water in the North, 29 ; 
probable consequences of lowering the depth of, 
29. 

Atmosphere and Meteorology, 206. 

Atmosphere. See Air. 

Attakapas of Louisiana, 145. 

Attraction of sun and moon, 99. 

Aurora Borealis, 314 et seq. 

Australia, icebergs south of, 50. , 

, tides at Port Essington, m, 115. 

Babel -Mandfib, Straits of, salt submailne current 

through, 9R 
Bahr-el-Assal, deposits at, 176. 
Ballybunion, the cliff of, 147. • 

Baltic, sand-banks of the, 169. * 

, the, in Celtic, Dead Sea, 124. 

Baltic Sea, ice in, 57. 

-, saltness of water in, 36. 

Banks and dunes, formation of, 159. 

Barometric observations, 217 ; diurnal oscillations 

of, 219. 
Bavarian Alps, vegetation on, 385. 
Beechey's observations of the tides, 110, 113." 
Belgium, the most thickly populated land, 444. 
Bidassoa, bar at the mouth of the, 161. 
Biesbosch, the forest of reeds, 154. 
Birds, extinct species of, 516. 
Black Sea, ice in, .58. 
, salt marshes of, 38. 



Blanchard Race, the, 116. 

Bore, or barre, 118. 

Borkum, lessening of the island of, 154. 

Breakwaters, natural, 151. 

Bremoutier on moving sands, 200. 

Bridet on the speed of hurricanes, 258. 

British Islands, climate of, 347. 

Calais and Dover, depth of water between, 27. 

Calcareous deposits at Ascension, 175. 

Calcutta, hurricane at, 253, 260. 

California, soundings off the coast of, 30. 

Canals, 500 et seq. 

Cape Ferret, changes at, 170, 171. 

Horn, icebergs south of, 56. 

Capri, grotto of, 145 ; color of water in, 42. 
Carentan, accumulations of mud in the gulf of, 173. 
•, ancient fjords at, 188. 



Caribbean Sea : saltness of water in, 36 ; clear wa- 
ter in, 41. 
Categat, the, depth of water in, 20. 
Catelet, hailstorm at, 312. 
Cattaro, mouths of, 130. 
Cazau, etang of, 197. 
Celebes and Gilolo, formation of, 185. 
Central American canals, 502. 
Charles Heddles, the ship, in a cyclone, 258. 
Chemical action on plants, 366. • 
Chesil Bank, of shingle, 164, 165. 
Chimborazo, vegetation of, 380. 
Chinese discovery of America, 87. 
seas, tides of, 107. 



Choa-Canzouni, islands of, 164 ; curious formation 

of, 183. 
Christiansand, fjords filling up, 137. 
Civilization, changes caused by, 457. 
of the East, early, 463. 



Cliffs, destruction of, 139. 

of France and England, 142. 

Climatal changes, 353. 

Climate modifying coast-lines, 135. 

Climates, 331 et seq. 

Clyde, the river, 495. 

Clouds and rain, 276. 

■, formation of, 280 ; height of, thickness of. 



282 ; aspect of, 283 ; classification of, 283. 
Coast-lines, modifications of, 127. 

ridges and sand-bars, 165, 167. 

Cod-fisheries, 398. 

Coins, found in stones at Elsinore, 174. 

Coirebhreacain, the, 117. 

Colors of sea-water, 41. 

Columbus, says, "£J iniundo es poco," 468. 

Combustion of rocks, 147. 

Copais, lake of, 479. 

Copenhagen, tidal current at, 124. 

Coral islands, 433. 

insects, 421 et seq. 

reefs, 421 et seq. 

in Tahiti, 424. 



Corfu, tides at, 123. 

Cretins, 447. 

Cryptogams or acotyledons, 357. 

Cultivation of land, 519 et seq. 

Currents of the ocean, 67; equatorial, 68; polar, 68; 
hot and cold, 73; of the South Atlantic, 82; In- 
dian Ocean, 83 ; Pacific Ocean, S3 ; Humboldt's 
Current, 84; disturbance in, 84; Tessan's Cm*- 
rent, 85; Rennell's Current, 88; secondary cur- 
rents, 88 ; the Bosporus, 89. 



532 



INDEX. 



Cycloues, 251 ; description of, 252 ; in the tropics, 
253 ; of Calcutta, in 1864, and of Havana, in 1S46, 
253 ; effect on forests, 253 ; in the Delta of the 
Ganges, 253 ; speed of, 257 ; rotation of, 259 ; ex- 
plosions of air during, 259; direction of, 203; the- 
ory of, 263 ; how to avoid, 267 ; local, 269. See 
also Whirhvinds and Hurricanes. 

Dantzic and Pillan, coasts of, 170 ; dunes between, 
204. 

Declination of the needle, 325. 

Deep sea, life in the, 417. 

Delibab of the Magyars, 211. 

Deroute Passage, the, 116. 

Destruction of various species of animals, 518. 

Dicotyledonous phanerogams, 357. 

Dikes, in Friesland, 487 ; at Sylt, 488 ; at West- 
kapelle, 488 ; at Point-de-Grave, 489 ; at Petten, 
491. 

Djerbah, tides at the island of, 122. 

Dollart, invasion of the waters of the, 154. 

Dover and Calais, depth of water between, 27. 

Dover, Straits of, 141. 

Dove's theory of the winds, 231. 

Drainage, 475. 

of lakes, 478 et seq. 

Drying up of bays and salt lakes, 175. 

Dun, origin of such termination in names of towns, 
such as Verdun, 196. 

Dunes : from decomposition of rocks, 187 ; forma- 
tion of, 188, 189 ; march of the, 191 ; crescent- 
shaped, 193; height of, 195; disasters caused by, 
199; ofGascony, 199; of Lege, 200; Bremontier's 
theory of, 200 ; arresting the progress of, 202 ; 
moving, of Brazil, 203 ; forests growing on, 203 ; 
ancient, of Medoc, 203 ; consequences of destroy- 
ing timber-growth on, 204; covering the, 204; 
fixation of, 205. 

Duperrey's Pacific current, 84. 

Dust whirlwinds, 273. 

Dynamic equatof, 330. 

Eager, the, or mascaret, 118. 

Earthquake waves, 30. 

Eastern Archipelago, origin of the, 181. 

Egripos, tidal current in Strait of, 123. 

Egyptian canals, 500. 

Electric telegraph, the, 505 et seq. 

Electrical phenomena, 313. 

ElsinorCj coins found in stones on the shore, 174. 

Emigration, 464 et seq. 

Encroachments of the sea, 140. 

English flora, the, 375, 390. 

Equatorial current, 68 ; of South Pacific, 84, 85. 

Equinoctial tides, 107. 

Erosion of cliff, 142, 143. 

Etang of Cazau, 197. ' 

Etesian winds, 239. 

Euripus, tidal current at, 123. 

Europe, climate of, 338, 339. 

Explosions of air during cycloues, 259. 

Extinct species of birds, 516. 

Bye of the tempest, the, 254. 

Faroe Islands, soundings near, 21 ; no flowering 
shrubs on, 366. 

Fata Morgana, the, 211. 

Fauna : number of species of animals, 393 ; relative 
abundance of, 395 ; oceanic fauna, 396. 

Fecundity of the ocean, 397. 

Fisheries : of the North Pacific, Japan, and the Ca- 
naries, 398. 

Fitzroy's classification of clouds, 283. 

, observations of the tides, 110, 113. 

Fjords: of South America, 131; Lysefjord, 130; 
mouths of Cattaro, 130 ; filling up of, 133 ; Swed- 
ish, 134; Norwegian, 134; Icelandic, 136;'Chris- 
tiansand, 137 ; Carentan,138. 

Floating marshes, 145. 

Flora, number of terrestrial, 357. 

of the Amazons, 377. 

, mingling of the, 381. 

Fluvial laws, diversity of, 125. 

Foehn of Switzerland, the, 243. 



Foraminifera, 400. 

Forbes's map of living organisms in the sea, 412. 

Forests, decay of, 359. 

Forviosa, ship, encounters floating iceberg, 54. 

Fortified towns, 459. 

Fucino, draining of lake, 478. 

Fuudy, tides in the bay of, 107. 

Franklih's test of the Gulf Stream, 80. 

Frigid Zone, life in, 441. 

Gain de flat, winnings from the waves, 142. 

Ganges, the bore in the, 119. 

Gascony, the dunes of, 200 ; fixed for the future, 205. 

Gases composing the atmosphere, 200. . 

Geological labors of insects, 421. 

Ghadames, sand mountain near, 188. 

Giants' caldrons, 144. 

Giens, peninsula of, 163. 

Gilolo and Celebes, formation of, 185. 

Glaciers of Greenland and Spitzbergeu, 49. 

Goodwin Sands, the, 141. 

Great Swatch, the, 30. 

Gulf Stream, 70 ; its course, 71 ; its color, 74; salini- 
ty of, 74 ; effects of, 74, 75, 79 ; fish in, 75 ; temper- 
ature of, 75 ; speed of, 70 ; debris carried on, 76 ; 
extent of, 77 ; submarine course, 78 ; Franklin's 
fears of, 80 ; knowledge of, utilized in navigation, 
81 ; of the Northern Pacific, 85. 

Gyrations of winds, 249. 

Hailstorms, 310 et seq. 
Halley's ]©agnetic chart, 324. 

theory of the trade-winds, 228. 

Harmattan, or burning wind, 235, 238. 

Harmony of Flora and Fauna, 407. 

Havana, no hailstorms in, 312. 

Havre, phenomenon of tides at, 114. 

Heat, needed by plants, 361. 

Heligoland, circular breakwater at, 152 ; changes in 

form of, 153. 
Herring-fisheries, 397. 
Hivernage, or winter season, 293. 
Holland, the dikes of, 483. 

-, encroachments of the sea, 153. 



Holyhead, tides at, 114. 

Homes of insects, 400. 

Homoiozoic zones, 413. 

Hooghly, the bore in the, 119. 

Horary variations, 348. 

Hours of day and night, 330. 

Howard's classification of clouds, 283. 

Huiranvucan, or hurricane, 251. 

Humboldt's Current, 84. 

Humming-birds at the crater of Pichincha, 416. 

Hurricanes: season of, in West Indies, 252 ; in the 
southern hemisphere, 252 ; in the Indian Ocean, 
252 ; calms during a hurricane, 254, 255 ; the great 
hurricane of 1780, 250. See also Cyclones. 

Hurricanes and whirlwinds, 251. 

Ice, formation of, 46; freed from miich salt, 47; 

fields of, 47. 
Icebergs : formation of, 49 ; size of, 51 ; movement 

of, 51 ; of Antarctic Ocean, 54. 

Ice-fields,' ^Itent of, 47 ; rapid disapp^rauce of, 48. 

Icelandic fjords, 136. 

Indian Ocean, depth of, 30 ; saltness of Water of, 

3T\ currents of, 82. 
Influence of climate on species, 401 et seq. 
Inishmore, clifls at, 149. 
Insects, homes of, 406. 
Inundations of the coasts, 153. 
Iquique, saline atmosphere near, 37. 
Irish Sea, tidal current in, 110. 
Irrigation, works of, 472. 
Islands and islanders, 453 et seq. 

, origin of, 179. 

Isochimenal and isotheral lines, 346. 

Isoclinal lines, 329. 

Isodynamic lines, 330. 

Isogonal lineSj 328. 

Isotheral and isochimenal lines, 345. 

Isothermal lines, 222, 341. 



INDEX. 



533 



Java, botany of, 3S1. 

Keys of Florida, 430. 

Kuro-Sivo, or Black River of Japau, S5. 

Kurrachee, tides at, 115. 

Laguues, consolidation of, 101. 

La Hogue, Tourville's disaster at, 116. 

Lakes, drainage of, 4TS. 

La Madeleine^ road of, 172. 

Lii'ge, dunes of, 200. 

Leghorn, tides at, 122. 

Lettes, or ledes, of sand, 192. 

Light necessary to plants, 363. 

replacing warmth, 367. 

Lightning splitting rocks, 306. 
Littoral ridges, formation of, 172. 
Lysefjord, Hugo's description of, 130. 

Machinery, total in the world, 504. 

Mavonne-bon-dicii, conglomerate, 175. 

Madagascar, origin of the island of, 1S3. 

, temperature of water off the coast of, 

44. 

Madreporic stone in Isle de Reunion, 66. 

Magellan Straits, tides in, 107. 

Magnetic equator, 326. 

poles, 326 et seq. 

Magnetism of the earth, 324. 

Man : dependent on climate, 434 ; solidarity be- 
tween, and earth, 435; antiquity of, 437 ; races 
of, 43S ; ancient and modern types of, 439; influ- 
ences of climate on, 440 ; local distribution of, 
443 ; influence of mountains on, etc., 445 et acq. ; 
influence of the sea and rivers on, 452 ; islands 
and islanders, 453 ; harmony between countries 
and inhabitants, 461 ; work of man, 466 et seq. ; 
influence on nature, 522 et seq. 

Maps of the world, ancient, 467. 

Marine grottoes, 145. 

Mascaret, the, or Eager, US. 

Mauritius, curious effects of cyclones at the, 271. 

Maury on the Gulf Stream, 70. 

Median zone, 413. 

Mediterranean : depth of the, 25 ; saltness of the 
water, 36 ; currents of, 90 ; supply of water in, 91 ; 
tides in some parts of the, 122 ; the flora of, 375. 

islands, origin of the, 182. 

Medusaj, 398. 

Messina, Straits of, 123. 

Meteorology and the atmosphere, 206. 

Mexico, sand mountains in the Gulf of, 188. 

Miasma of marshes preventible, 514. 

Mice living in snow, 402. 

Microscopic organism of the sea, 398. 

Miquelon, islands of, 164, 166. 

Mirage, the, 210. 

Mississippi, slight tides of, 112. 

Mistral, or Master, the, 244. 

Mists, formation of, 280. 

Monocotyledons, 357. 

Monogenists, 437. 

Monsoons of India and Arabia, 236. 

Mont Cenis Tunnel, 499. 

Moskoestrom or Maelstrom, 118. 

Mount St. Michael, tides at, 107. 

Mountaineers, patriotism of, 449. 

Mountains, vegetation on, 379 et seq. ; animal spe- 
cies found on, 416 ; influence on life, 446. 

Mozambique Channel Current, S3. 

Miihry's theory of the winds, 231. 

Nature, man's influence on, 522. 
Needle, polar, 324 et seq. 

Newcastle-upon-Tyne, depth of water near, 26. 
New Zealand, origin of, 182 ; icebergs south of, 50. 
Noirmoutiers, tides in the Straits of, 109. 
Nordstrand, island of, 155. 
Norfolk Island, origin of, 182. 
North Sea, average depth of, 26. 
Norway, reclaiming marshes in, 474. 
Norwegian fjords tilling up, 134. 

mountains, vegetation on, 384. 

Nossi-Mitslou, formation of, 183. 



Ocean, the: importance of, 17; influenceof, 17; mod- 
ifying coutiguratiou of the globe, 18 ; the bottom 
of the seas, 20 ; sedimentary deposits in, 21 ; pro- 
verbially fathomless, 22 ; estimated depth of, 23 ; 
generally deep at the base of abrupt mountains, 
25 ; soundings in the North Atlantic, 28 ; Maury's 
"telegraph plateau," 2S; consequences of low- 
ering the depth of the North Atlantic, 29 ; depth 
of the South Atlantic, 29 ; earthquake waves in 
the Pacific, 30; immense depth of the Pacific 
Ocean, 30 ; depth of the Indian Ocean, 30 ; depth 
of the Red Sea, and Bay of Bengal, 30 ; the In- 
dian Archipelago and Antarctic seas, 31 ; mean 
depth of the mass of marine waters, 32 ; extent 
of total surface of the ocean, 32; differences of 
level in several seas, 33 ; composition of sea-wa- 
ter, 35 ; mean specific gravitie&pf, 35 ; substances 
found in the waters of, 39 ; JBors of, 41 ; tem- 
perature of, 43. ^W 

Oceanic telegraphs, 506. 

vegetation, 370, 371. 

Oesel, united to main-land by ice, 57. 

Omar, describes the tides, 123. 

Ondavorology, 139. 

Orne, bank at the mouth of the, 162. 

Oued-Gabes, tide at the mouth of, 122. 

Oyster culture, 507. 

Pacific Ocean : depth of, 30 ; earthquake waves of, 
SO ; currents of, 83 ; equatorial current of, 84. 

Pampero, the, of La Plata, 208. 

Panama, tides in bay of, 107. 

Patriotism of mountaineers, 449. • 

Peacock, ship, in the ice, 55. 

Pelasgian plants, 396. 

Peninsulas of Cape Sepet, Giens, Quiboron, and 
Monte Argentaro, 163. 

Pentland, Firth, the, 118. 

Persian Gulf: depth of, 30 ; tides in, 107. 

Pesquiers, laguue of, 162. 

Phanerogams, 357. 

Piddington names the cyclone, 251. 

Pilot charts of Maury, 226. 

Plants of various climates, 361 et seq. 

Polar auroras, 314 et seq. 

carrents, 68. 

Polders of Haarlem, 480. 

Polluted streams, 476. 

Polygenists, 437. 

Popocatepetl, vegetation of, 380. 

Porquerolles, island of, 162. 

Pot-au-Noir of tropical rains, 292. 

Potamogetons, 368. 

Protective disguises of animals, 404. • 

Railways, 496 et seq. 

Rain : caused by wind, 285 ; caused by mountains, 
287; average fall of, 287 e^ seq.; tropical rains, 
292 ; rainy and dry seasons, 293 ; winter rains, 
297; of the polar regions, 299; rainless countries, 
300 ; erosive action of, 303 ; distribution of, 337. 

Red Sea : depth of, 30 ; saltness of the water, 37 ; 
evaporation and supply of water in the, 91 ; coral 
reef of, 429. 

Rennell's Current, 88. 

Rocks: undermining of, 147; combustion of cliffs 
at Ballybunion, 147 ; varieties of, 148 ; cliffs at In- 
ishmore, 149 ; broken, destroy animal and vege- 
table life, 150 ; formation of, 174. 

Rollings of a ship, 00. 

Rorqual seen by Scoresby, 396. 

Ross, Sir John, at northern Magnetic Pole, 326. 

Sable Island, the dunes of, 198. 

Salt-works of Trapani, 485. 

Sand-banks of the Baltic, 169. 

Sands, varied aspects and colors of the, 177. 

Sargossa, or grasses of the tropics, 370. 

Scarabreus living in hot water, 402. 

Scylla and Charybdis, 123. 

Sea of Haarlem, draining the, 479. 

"Sea of Milk,". 399. 

Sea-locks and fjords, 129. 

Sea-ports on rivers, 125. 



534 



INDEX. 



Sea-water : composition of, 35 ; mean specific grav- 
ities of, 35 ; substances found in, 39 ; colors of, 
41 ; temperature of, 48. 

Sea-weed for manure, 509. 

Seals, destruction of, 517. 

Seine, the bore in the, 119. 

Severn River, tides at the mouth of, 107. 

Sewage-water, necessity of, 477. 

Seychelles Islands, origin of, 1S2. 

Shakspeare Cliff, 151. 

Shallows of the coast, 173. 

Shipwrecks, prevention of, 511. 

Shores, normal form of, 156. 

Silver in sea-water, 39. 

Simoon, the, 242. 

Skeleton from the tufa of Guadaloupe, 174. 

Skulls, human, 436^ 

Soils favorable to attain plants, 369. 

Solar rays, action off plants, 365. 

South Atlantic, currents of, 82. 

St. Helena, the flora of, 391. 

St. Thomas, great hurricane at, 260. 

Stones, whirlwinds of, 274. 

Storms, eflects on coasts, 139. 

Streams unclean, 476. 

Suez Canal, 501. 

Swedish fjords filling up, 134. 

Swiss mountains, vegetation on, 383. 

Sylt, island of, 155. 

Tahiti : tides at, 112 ; coral reefs of, 424. 

Tedjura, deposits in the Gulf of, 176. 

Tehuantepec, carral through, 502. 

Telegraphs of the world, 505 et seq. 

Temperate zone, life in, 442. 

Temperature, average of, 352. 

of the ocean, 43. 

Tenerifi'e : atmosphere of, 230 ; vegetation in, 382. 

Terrestrial magnetism and temperature, 330. 

Tessan's Current, 85. 

Thermal equator, 341. 

Thermometers and barometers, observations with, 
217. 

Thermometric observations, 354. 

Thirst of the Gazelle, or Mirage, 211. 

Thorsnuten, elevation of coast at, 129. • 

Thunder, where it is never heard, 307. 

Thunder-clouds, their formation and height, 305. 

Thunder-storms : most frequent, 306 ; none in Peru 
or Bolivia, 307 ; of Western Europe, 308 ; immu- 
nity of trees, 310 ; commence at the hour of high- 
tide, 312. 

Tidal Currents : in the Irish Sea, 116 ; the Blan- 
chard Race, 116; the Deroute Passage, 116; the 
Great Gulf or Coirebhreacain Passage, 117 ; the 
Pentlaud Firth, 118 ; the Moskoestrom or Mael- 
strom, 118 ; the bore, barre, eager, or mascaret, 
118, 119 ; of the Mediterranean, 122, 123 ; at Euri- 
pus, or Strait of Bgripos, 123 ; Omar describes the 

; tides, 123 ; in the Mediterranean, 123 ; in the Zuy- 
der Zee, 124 ; in the Baltic, 124 ; in the harbor of 
Copenhagen, 1-24 ; at Wismar, 124 ; differences of, 
125. 

Tidal Waves : lunar and solar, 99 ; Whewell's and 
other theories, 102 ; general character of, 107. 

Tides, the, 94 ; Laplace's theory of, 96 ; Whewell's 
theory of tidal waves, 102 ; at Mount St. Michael, 
107 ; in the Severn River, 107 ; in the Chinese 
seas, 107 ; in the Persian Gulf, 107 ; in the Bay of 
Fundy, 107 ; the equinoctial, 107 ; in the Bay of 
Panama, 107 ; tidal waves, 107 ; in the Straits of 
Magellan, 107; in the Straits of Noirmoutiers, 



109 ; Fitzroy's and Beechey's observations on the, 
. 110, 113 ; at Tahiti, 112 ; at the mouth of the Missis- 
sippi, 112 ; at Kurrachee, 115 ; at Port Essington, 
Australia, 115 ; at Havre, 114 ; at Holyhead, 114. 

Toilers of the Sea, scene of, 117. 

Torghatten, rock of, 145. 

Toroses of the Siberian coast, 48. 

Tou7-mentes, or tempests, 244. 

Trade-winds, the, 224 ; counter, 228. 

Transalpine railways, 499. 

Trapani, salt-works of, 485. 

Traveling and commercial nations, 452. 

Trees, destruction of, 518. 

Tropical forests, 376. 

zone, life in, 440. 



Turbaries, 368. 
Typhoons, 251. 

Underground heat, 333. 
Undermining of rocks, 147. 

United States : flora of the, 390 ; unoccupied land 
in the, 470. 

Vegetation : influences on, 361 ; zones of, 374 ; on 

mountains, 379. 
"Vegetation versus sand-hills, 202, 
Venice, lagunes and lidi of, 168. 
■, tides at, 122. 



Vents alizes, or trade-winds, 225. 
Volcanic slopes, cultivation of, 471. 
Volcanoes, miniature, 178. 

Wangerooge, island of, 154. 

Water-spouts, 275. 

Waves of the sea, 59 ; height of, 61 ; breadth of, 62 ; 
speed of, 62 ; depth of moving, 63 ; heiglit to 
which crests attain, 64 ; force of, 64. 

Wells regulated by flow of the sea, 145, 

Whales: size of, 396; destruction of, 517. 

Whewell's theory of the tidal wave, 102. 

Whirlwinds : the cause of, 270 ; of Malauny and 
Monville, 271 ; of dust, 273 ; of stones, 274 ; wa- 
I ter-spouts, 275. See also Cycloiies. 

Winds : geological agents, 208 ; keeping back tides, 
208 ; work performed by, 209 ; circulation ofj 223 ; 
trade -winds, 224; oscillation of, 227; counter 
trade-winds, 228 ; bearing dust and ashes, 228 ; 
returning currents of, 229 ; Dove's and Miihry's 
theories of, 231 ; directions of hot and cold winds, 
231; trade-winds of the continents, 235; mon- 
soons of India and Arabia, 236 ; Etesian winds, 
239 ; land and sea breezes, 240 ; breezes of the 
French Alps, 241 ; atmospheric tides, 241 ; the 
Wisper-wind, 242 ; the solaures of the Drome, 242 ; 
the simoon, 242 ; the Swiss Foshn, 248 ; tourmen- 
tes, or tempests, 244; the mistral or "master," 
244 ; zones of variable winds, 245 ; mean direc- 
tion of, 247 ; westerly winds in France, 248 ; gy- 
rations of the wind, 249 ; aerial eddies, 251 ; cy- 
clones and hurricanes, 251 ; speed of hurricanes, 
257; the cause of whirlwinds, 270 ; forming rain, 
285. 

Wismar, tidal current at, 124. 

Wisper-wind, the, 242. 

Work of man : exploration of the globe, 466 ; as- 
cents of mountains, 469; agriculture, 470; irri- 
gation, 472 ; culture of marshes, 474 ; drainage, 
475 ; draining lakes, 478. 

Zante, tide at, 123. 

Zuyder Zee, the, 481 ; tides in the, 124. 



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